I realize these are essentially two questions (though I'm guessing it reached Japan after it was fetishized), but I'm not finding much believable information on either, just unprofessional blogs with no citations. Any leads?
I'll only try to address the origin of the French maid costume. It's still incomplete so people with knowledge of fashion and fetish wear can provide more information about its dissemination in popular culture.
[Warning: lots of NSFW stuff below]
In French, the "French maid costume" is called the costume de soubrette, which is much more indicative of its fictional status.
The soubrette
The soubrette is a comedic stock character of French theatre, used notably by Molière, Beaumarchais and Marivaux, and derived from, or at least inspired by the Columbina character in the commedia dell'arte. The soubrette is a house servant, often a chambermaid, sometimes a woman in a slightly higher social position, such as a lady in waiting. She is witty, sassy, down-to-earth, outspoken, strongly dedicated to her mistress that she helps to find love, and she occasionally finds love herself. The soubrette is preferably young (but not always if she's supposed to be experienced) and attractive: "the part demands a pleasant appearance", wrote Larousse's Dictionnaire universel in 1875. She must be pretty enough to be able to swap places with her mistress if the plot requires it, like Lisette in Marivaux's Le Jeu de l'amour et du hasard.
Unlike her mistress, the soubrette does not have to keep the appearance of modesty. The attributes associated to her character not only underline her vivaciousness and graciousness (accorte, charmante, piquante, mutine) but also her sexual frankness: she is gaillarde, friponne, délurée, etc., all things that her mistress cannot be due to her higher social status. The soubrette has a costume that makes her attractive (though not the costume currently known as the "French maid" one). In Molière's Tartuffe, the eponymous pious fraud has a look at Dorine's cleavage:
Cover up that bosom, which I can’t
Endure to look on. Things like that offend
Our souls, and fill our minds with sinful thoughts.
Not everyone appreciated the character: the entry for Soubrette in Diderot and d'Alembert's Encyclopédie in 1765 said that the soubrette was
wicked, talkative, without decency, without feeling, without morals, & without virtue; for there is nothing in society that resembles this character.
The soubrette is fictional but the character cannot be separated from the two categories of women it was closely associated to: the actresses who played the part, and the house servants. Those two groups were highly eroticized, both in real life and in their representation.
Actresses
In the case of actresses (and more generally female stage performers such as dancers and singers), the frontier between entertainment and sex trade was extremely permeable throughout the 19th century, as demonstrated for instance by the records of the Police Prefecture in the 1860-1870s, which shows actresses being overrepresented among courtesans (Houbre, 2006). Female stage artists often engaged in some form of sex work or had to submit to sexual coercition by theatre managers or other actors. Women who were primarily sex workers turned to the stage for additional revenue and exposure. Until the early 1900s, for the public, the distinction between actresses and courtesans was paper thin (Martin-Fugier, 2016). While the soubrette was a prestigious part when played at the Comédie-Française, it could also be an entry-level stock character that often did not require much more than being pretty, and as such it provided a potential path to the stage for the less talented. Alice Lavigne, a small-time courtesan, had a dual career as a theatre soubrette, and the Gil Blas could write in 1879:
Mlle Alice Lavigne has found a way to make people laugh in a role of a soubrette, which does not have thirty lines.
In 1842, Jeanne Duval, not yet Baudelaire's long time mistress, tried to start an actress career as a soubrette, but, as narrated by photographer Nadar decades later, she was poorly received by the public, who booed her due to her unusual appearance: people did not expect a soubrette to be tall and dark-skinned (Nadar, 1911):
In the consecrated dress of a soubrette, the little apron and the cap with floating ribbons, a tall, too tall girl who exceeds the ordinary proportions by a good head, especially for this part, is already surprising. But this is nothing: this extra-large maid is a Negress, a real Negress, a mulatto at least, this is indisputable: smearing packs of white make-up do not make paler the copper of her face, neck, and hands.
Duval quit acting after a few days (Reynaud, 1917).
Maids
Anne Martin-Fugier, in her book about (actual, not fetishized) French maids in the 19th-early 20th century La place des bonnes, dedicates a whole chapter to their sex lives. Maids started young and those who worked in the cities often came as teenagers from the countryside (Martin-Fugier, 2014). Becoming a maid offered a promise of upward mobility, thanks to good wages and education, and 30% to 50% of the maids who eventually married experienced a rise in their social status (MacBride, 1976). However, the path through marriage was difficult, and fiction as well as medical and police records concur in drawing a rather dreadful picture of the condition of female servants: many maids were sexually exploited by their masters and fellow servants, who considered that being a bonne à tout faire (maid-of-all-work) included sexual duties. Those relations, consensual or not, resulted in illegitimate/unwanted pregnancies, backroom abortions, transmission of venereal diseases (syphilitic maids in charge of a family's chidren were a cause for concern, see Commenge, 1897), and, at worst, infanticides, suicides, and murders.
This made the position precarious: a pregnant maid, or a maid with child, was considered as useless, and could be summarily dismissed unless she abandoned the child or have it raised by a wet nurse in the countryside, if she could afford it (the cost of a wet nurse could quickly consume a maid's wages). Many maids, after being raped or abandoned by their seducer, lost their job and turned to prostitution for survival. In a survey taken by Alexandre Parent-Duchâtelet among Parisian prostitutes in the 1830s, one third of them told that the seduction-abandon-dismissal sequence was the main reason for becoming a prostitute. Later in the century, French physicians who specialized in treating prostitutes had a similar conclusion (Martineau, 1885; Commenge, 1897).
This situation led to a duo of conflicting stereotypes: the maid was both sexual victim and a temptress, she was "corrupted and corrupting" (Boureau, 1995). Being of lower extraction, maids were judged to be "naturally" more sexual and promiscuous. The clichés about chambermaids, wrote Gustave Flaubert in his Dictionnaire des idées reçues, were that they were "always prettier than their mistress" and "that they were always dishonored by the son of their master". The narrative of the maid seduced by her master (or mistress!) or by his son, or "initiating" the young man to sex - a cheap and practical alternative to the brothel - was an easy source for comedy or drama throughout the 19th and 20th centuries.
More generally, the perception of maids as promiscuous and sexually available (for free!) was the fodder for erotic fantasies explored in countless works of fiction. In the mainstream works of Maupassant, Flaubert, and so many others, as well as pornographic literature (e.g. the Victorian memoir My secret life, 1888), the male heroes consider maids as easy and natural preys, always up for a good romp if you ask them, and a man does not have to ask anyway. In Maupassant's short story Un fils (1882), the narrator, travelling in rural Brittany, stops at an inn where he finds himself turned on by the local girls:
The girls, tall, handsome and fresh have their bosoms crushed in a cloth bodice which makes an armor, compresses them, not allowing one even to guess at their robust and tortured neck.
He then tries to rape the inn's 18-year-old chambermaid, who resists him:
I abruptly seized her round the waist, and before she recovered from her astonishment I had thrown her down and locked her in my room. She looked at me, amazed, excited, terrified, not daring to cry out for fear of a scandal and of being probably driven out, first by her employers and then, perhaps, by her father. I did it as a joke at first. She defended herself bravely, and at the first chance she ran to the door, drew back the bolt and fled.
But, a few days later, the young woman comes to the man's room at midnight, and, of course, she is the one to initiate sex. Not that this encounter was found remarkable for the narrator...
A week later I had forgotten this adventure, so common and frequent when one is travelling, the inn servants being generally destined to amuse travellers in this way.
This cartoon by Henry Fournier from 1933, published in the erotic magazine Séduction, shows how normalized this could be.
In real life as in fiction, consequences for the rapist/seducer were minimal, and only the maid paid the true price for her "seduction". In Maupassant's story, we learn that the maid died after giving birth to the son of the narrator.
-> Part 2
Ah yes, the real questions being asked on this sub that are important enough to pull me away from the Classical Chinese texts I should be studying right now past midnight.
Going off of u/gerardmenfin excellent and comprehensive covering of the costume, I can briefly go over the history and social importance of the lolita aesthetic in Japan.
Since the opening of the country during the Meiji period of Japan, part of the wide social changes that swept Japan was the education of women, which led to stronger means of expression their own language and culture. In the 1900's, young girl or Shoujo magazines and comics were popular among educated women. This would clash with traditional interpretations of femininity and gender expectations. With the social restraints of the war period in the 30's and 40's however, popular culture and expression was heavily limited and regulated. Trends spread again beginning in the 70's and 80's, when the post war economic boom and loosening of regulations provided fertile ground for Japan's development of subcultures and media.
Lolita aesthetic is part of the general "cute" or "kawaii" shoujo, or young girls popular subculture in Japan, which began spreading in the 1970's. Much of shoujo can be understood as a type of "counterculture" or "counterpublic", as a way of expressing self against a male-dominated public space with rigid structures and standards of acceptability and normality. For instance, handwriting utilized flourished and loopy letters to emphasize cuteness. There was also gyaru aesthetic and speech, which challenged beauty and speech standards with innovative makeup and usage of "masculine" forms of speaking (the pronoun boku instead of atashi). Another is the yankee style* that corresponded with bosozoku motorcycle youth, with girls dying their hair, using extravagent makeup, wearing gaudy clothes, and forming gangs.
As for the Gothic/lolita style, the visual-kei or visual-style genre of rock music saw elaborate fashion, make-up, and costumes. Groups such as X Japan and Malice Mize pioneered these looks, with their music and appearance coinciding with a time when many became disillusioned with the bursting of the economic bubble. Manga, anime, and film spurred growth, examples include Paradise Kiss, Chobits, Yuki no Kurenai Keshou, *Shoujo Bara Kei, Kozetto no Shouzou, Rozen Maiden,Kore ga watashi no goshujin-sama, and Shimotsuma monogatari. Manifesting with Victorian/Edwardian doll attire and western goth aesthetic, these styles allowed women to explore contrasts of youth and innocence with cynicism and melancholy. The elaborate dresses of European aristocratic wear allowed women to identify themselves as sophisticated, "princesses" in a way, with a wide variety of interests and hobbies.
There are different styles within Lolita culture, all derivatives of the Classic or Traditional Lolita, which is founded on Victorian dolls as well as Alice in Wonderland. Dresses deemphasize bust and hips with flattened bodice, high waistlines, and full skirts. White, pastel, and floral colors are dominant. From there two main categories emerge, the Sweet Lolita or ama rorita, and Goth Lolita. Sweet Lolita is associated with kawaii cuteness, and draws heavily on Victorian, Rococo, and Romantic excess. The Classic Lolita is essentially exaggerated. The body figure is once again deemphasized with flat bodices, high waistlines, and full knee-length skirts, colors are soft and light, usually solid. Accents include bows, ruffles, and laces, with accessories such as purses, parasols, and hankerchiefs. Goth Lolita incorporates traditional Victorian elements with mourning clothes and western Goth aesthetics. Clothing is similar to Classic and Sweet Lolitas, though skirts may vary in size and height. Black is the obvious prime color, with accents of white or red. To emphasize the Goth style, accessory might vary with a worn and bruised teddy bear or coffin or leather purse.
It's important to understand the relationship between Nabokov's Lolita and Japanese Lolita. Japan redefined it to emphasize qualities of modesty, innocence, gracefulness, politeness, and cuteness. In extension, this connects to ideas of empathy, compassion, infantilism. It's a perspective leaning into youthfulness, sensitivity, and humaneness, but also embracing a foreign, Western, old-fashioned, and "nostalgic" feel, which all stands starkly against the power hierarchies of Japanese society. That vulnerability reflects a conscious or subconscious apprehension towards the loss of youth and innocence. Clinging to shoujo is a rejection of Humbert-like defilation and deflowering, rejection of being reduced to a sexualized object and body. But cuteness also highlights and emphasizes one's own beauty and attractiveness, dolls as an idealized form of lovable pure youth. Lolita is meant to be empowering and strengthening, affirming ones appeal and sexuality in a unique way.
Inevitably, much sexual attention has been placed onto the subculture, clashing with the original intentions of the movement and leading to varying depictions, interpretations, misinterpretations, and misrepresentations in popular culture. Cosplay is one such issue. Many Lolita take issue with cosplay, as it is considered a "mimicking" of the character, as dressing up rather than embodying. Lolitas consider their Lolita self as true and natural, cosplay is imitation and not genuine.
While there are outwards appeal to Lolita, a major part of the culture is the ritualized performance, how one behaves and speaks. This allows Lolitas to experience and celebrate themselves in a space outside of established social norms. In speech, Lolitas are careful to be communicate slowly, courteously, humbly, concisely, and polite when answering positively and indirect when answering negatively. Vulgarness is strictly avoided.
There is much much more that can be said about Lolita culture. In particular, the issues of sexualization and commodification with "lolicon" or "lolita-complex". But I hope I've provided a decent overall explanation of Lolita culture in Japan. The heyday of street fashion has passed, but Lolita remains influential and popular in public consciousness and media. Lolitas reflect a strong expression of women seeking to maintain their sense of self, value, femininity, individuality, and uniqueness in the face of a demanding and society and structure. It's a form of empowerment, resistance, and agency, while also exploring ideas of nostalgia, sexuality, and individuality.
References and Further Reading: