I can speak to part of this (namely vestments in the Western Christian Church).
In the early days of the Church, clerical dress was not noticeably different from what you might call upper-class streetwear. In The Early Church, Henry Chadwick relates that
...in the West the clergy did not wear distinct dress, even when officiating at services. In a remarkable letter of 428 Pope Celestine I rebuked clergy in southern Gaul for disturbing innovations in this respect. Western 'vestments' originated simply in the ordinary secular costume of antiquity, preserved by conservatism in churches after it had been abandoned elsewhere. (164)
So that is part of the answer. But why did this conservatism preserve them in churches but nowhere else? In part, the vestments began to acquire layers of spiritual/symbolic meaning, as related in The New Altar Guild Book:
All three lines of liturgical wear [for bishops, priests, and deacons] have been adopted and adapted, added to and subtracted from, by clergy though subsequent centuries according to the customs and resources of their times and places. Although their "daily wardrobe" of the early years stayed the same, there is evidence that leaders reserved their "best clothes" for Sunday. They also set aside different sets of garments for different roles in the liturgy. When the clothing became "vesture," it was progressively decorated with symbols, at first simply and then more elaborately--adding to the visual learning aids already developing in other church furnishings. When knowledge of the historical origin of the garments had faded from actual memory and become folklore, allegorical ideas and some religious meanings were thought of for many of them. (70)
Although the symbolic meanings for liturgical garments were not original to the garments, many throughout history have found them compelling. Moreover, clerical vestments serve as instant identifiers. If an ordained person is vested, those in the know can tell at a glance whether he is a bishop, priest, or deacon, and even whether he is Catholic, Anglican, Orthodox, etc. Differences in styles of vestments or ways of wearing them can also signal one's allegiance to various liturgical parties within the Church -- for example, a "high church" Anglican priest will vest for the Eucharist in a chasuble, whereas a "broad church" priest might wear a cassock and surplice, and a "low church" priest just his clerical collar and a stole.
Of course, clerical vesture has continued to change over the centuries and no doubt will continue to do so. Many churches do not use vestments. The move away from vesting in most of today's Protestant churches can be traced back to the Puritan movement in England in the 1600s. Stephen Neill writes, in his book Anglicanism, that
The Puritan was concerned for the prophetic ideal of holiness -- and exacting ethical code, and an adoring submission before the majesty of God. To him the wearing of the surplice was a bowing down in the house of Rimmon [Baal], an unworthy compromise with 'the mother of harlots' [i.e. those awful Catholics]. (143)
The Purtians preferred plain dress for their clerics, and in modern churches that trace their development from the Puritans there tends not to be any formal vesture for their clergy. A pastor may preach in a jacket and tie, for example, but the jacket and tie he wears to church will not be any different than the ones he might wear to the office.
I suppose that this answer doesn't really cover the when of your questions, except to say gradually and a long time ago. But I hope that it has provided some insight into the why aspect.
Sources:
For further reading:
Can I ask a follow up question? Thinking specifically about the pope, it almost seems like the way he dresses is a logical extension to the fashion of the rest of the clergy. Is this an artifact of a given time (e.g. They've just been wearing the same clothes since the C16th) or did somebody actually sit down at some point to standardize the entirety of Catholic dress?
I can speak specifically to some of the Jewish practices. This is a very wide ranging topic and I will only touch on the most salient religious aspects of these practices. There are other sociological aspects that I can't speak much to.
The main religious reason that orthodox Jews dress the way they do is because of the prohibition of Khukat Hagoyim ("the ways/traditions of the nations"), from Leviticus 20:23:
Do not follow the traditions of the nation that I expel from before you, for they did all of these and I was disgusted with them.
This is not just about dress, but in all practices of non-Jews. That Jews are only allowed to adopt non-Jewish practices if they are for a discernible practical purpose (that doesn't otherwise violate Jewish law). This is spelled out in Shulchan Arukh, Yoreh Deah 178.
The important part here is the explanation of The Rama (16th century). The Rama's decisions are what most Ashkenazi (broadly, northern European) Jews follow. He draws on two different understandings of this mitzvah (commandment):
However, The Rama states, if something that has a known origin and a practical purpose (e.g. tradesmen's clothing such as a doctor's coat), it's permissible. There were however strong customs as to what different religions wore in different regions, and it would be assumed that everyday dress followed these customs, that if a Jew went out to buy clothing that only Calvinists wore, that they were in violation of this mitzvah. In modern times this only comes up with clothing for particular religious practices (nun's habit, monk's orange robe, etc.) but used to be very prevalent for regular old people. (this will be relevant later)
In the 20th century, non-hasidic orthodox Jews generally follow the rulings of Rabbi Moshe Feinstein. He ruled more toward The Maharik on clothing, that so long as you aren't dressing out of a desire to imitate gentiles and the clothing is modest, then you can assume that you can wear it; that in modern times no one makes clothing and says "ah yes, this clothing is just for gentiles". People make clothing for everyone. Reb Moshe is why modern and centrist orthodox Jews will wear jeans, etc. while most hasidic Jews will follow the more stringent opinion that includes The Ran along with the (usually more stringent) opinion of the rebbe of their particular hasidic dynasty.
I hinted at this earlier, but there is also the issue of tzniut/tznius (modesty). Tzniut is about being modest not just in the way Jews look but in the way that they act. So while orthodox Jewish men are technically allowed to wear certain clothes, they don't because other men don't. If one person wore a flashy suit but no one else did, then that would be considered not tzniut. In many communities, the standard of dress for men is a black suit (maybe a deep charcoal), and if someone within that community wore a non-black suit it would be seen as immodest and vain.
In particular to hasidic sects, their whole outfit is usually particular to their dynasty. Within each dynasty they wear a particular type of black hat, a particular shtreimel, a particular bekishe, gartel, etc. How the specific customs of dress came to be adopted by each of these dynasties is a rabbit hole I haven't jumped down (and there's a dearth of available English literature on these things; it's mostly in Yiddish).
All of these practices probably have just as much to do with identity as anything else. With general orthodox populations too, identity and assimilation are big areas of concern, and distinctive dress is a way of promoting and reenforcing one's identity. Orthodox Jews know this and talk about it in explicit terms regularly, so it's not some underlying sociological phenomenon; it very much underlies and overlays. There is a lot penned on this aspect of the subject, but I am unfamiliar with it and won't conjecture further here.
Additional Sources:
Edit: formatting, typos
I'm especially interested in the Amish if anyone has that answer, as well. It seems they use tech up to some date and then stop. Was the at a decision made my a leader of the sects at that point in time or did a later leader mandate they roll back to a date?
I'd like to know why monks shave the top of their heads? Did a high level monk, who was bolding, make everyone shave the top of their heads to make himself feel/look the same as everyone else?
Hello everyone,
In this thread, there have been a large number of incorrect, speculative, or otherwise disallowed comments, including many asking about the deleted comments, which merely compounds the issue. As such, they were removed by the mod-team. Please, before you attempt to answer the question, keep in mind our rules concerning in-depth and comprehensive responses. Answers that do not meet the standards we ask for will be removed, and posters who break the rules of the subreddit admonished as applicable.
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