Your question calls for two separate, yet equally important, discussions: the history of diarying and the history of the relationship between diarying and femininity. Both of these topics are incredibly broad, as well as inherently cultural, meaning that the insights I am about to provide are narrow as I’m speaking mostly about western European cultural conceptions, and probably even more specifically, about Anglo understandings. I’m sure those with different specialties could speak to different cultural conceptions.

Lets start with the practice of keeping a diary, or what I often refer to as “diarying.” The practice of keeping a diary is not, necessarily a product of the modern era, but pre-modern diaries, especially those kept mostly by the clergy and nobility of earlier times would not resemble the type of diary you’re probably most familiar with. These earlier diaries, often referred to as annals, are more akin to the account book or timeline. They record important events often without the descriptive and introspective style of a more modern diary. Perhaps most importantly, these annals were simply a list of important events, and as such, were most commonly produced by the clergy and nobility as a way of recording a timeline. Although they were thought of a list of facts, they were often skewed and intended to highlight the major victories and general good doings of the church and aristocracy. They worked sort of like propaganda and new rulers often had these annals amended to reflect a version of “history” that better suits their agenda. There are of course exceptions; however, the vast majority of laboring people did not keep diaries not only because they could not read and write, but also because the very idea of keeping a running account of one’s thoughts and ideas was not common practice.

As with many critical cultural changes, the Enlightenment and growth of humanistic thought helped birth the practice of diarying. An increasing emphasis on education spread beyond the clergy and nobility during this period as a growing mercantile class both produced and demanded written material. It is not surprising that diarying became more widespread as more people could read and write.

But perhaps more importantly, the growth of diarying reflects not just a growth in literacy, but an increasingly popular sense of individualism. As literacy rates increased, among both men and women, so too did the innate desire to record personal thoughts, ideas, and experiences. It is really hard to quantify and explain such an intangible want or need, but scholars have connected it to the cultural importance of the individual and the Reformation. This topic is incredibly complex, and I not want to get too bogged down in the weeds, but an excellent primary source is Pierre Bayle’s Historical and Critical Dictionary (1697). Although Bayle’s groundbreaking work is complex and disorienting, one of the most prevalent features is his overt skepticism based on a distrust of authority and a Kantian belief in reliance on one’s personal right to judge. The modern diary reflects this epistemological change among western Europeans.

Beginning the late seventeenth, but really intensifying during the eighteenth century, diarying became not just an expression of enlightened individualist thought, but also a mark of refinement. There are many different forms of diaries that became popular in the mid to late eighteenth century, but importantly, almost all of these diaries blurred the line between public and private. Rather than the image of a diary locked away in drawer, diaries were often red aloud at gathering as a form of entertainment and as a way of demonstrating one’s sensibility and refinement. Some diaries were more akin to the popular epistolary novel and read like a series of letters to an anonymous reader. Diaries were (and still are) viewed as cathartic, and many important political figures and common people kept a diary as a way of relieving stress. In addition, the idea of the professionally trained historian really only began to emerge in the early twentieth century, and so many diary keepers kept and preserved their diaries as a way of informing future generations—mostly family members—about the times in which they lived.

It is important to have this background to fully understand how gendered conceptions of manliness and diarying came to be interconnected, or I guess opposed. First of all, I think it is important to note that I do not quite agree that twenty-first century people see diarying as inherently unmanly or effeminate. Perhaps it would be more correct to say that diarying is perceived as more popular among women than men, which is of course much different.

The association between women and diarying is inherently linked with its growth of diary keeping during the late eighteenth century and its performative elements. Importantly, during this same period, women (especially mercantile and upper-class women) were increasingly relegated to the home, or the “domestic sphere,” as the idea of the “cult of domesticity” became more prominent. Again, not to get dragged into the weeds, but basically this idea stressed the difference between the public sphere of men, which included labor outside the home and politics, with the domestic sphere of women, which was defined as house keeping and childrearing. There is a lot of debate whether the cult of domesticity was misogynic and forced upon women, or whether women were able to exploit the cultural conception to achieve their own ends, or both; however, what is clear is that eighteenth and nineteenth-century people understood the domestic sphere was an incredibly important societal space, especially because it was in the home that children raised and mothers who did the rearing included the raising of children. Because the nation relied on virtuous men, mothers were vital in the success of the nation.

So how could wives, mothers, and future wives and mothers demonstrate that they were worthy of such an important position? One way was through diary keeping. In her diary, a woman could demonstrate her refinement. Although it was inappropriate to publically discuss politics, she could record her thoughts in a diary. She could reflect on what she had read. She could record how she felt about the goings on in the family. The diary was seen as a natural place where she could reflect on and record her thoughts about the domestic sphere.

There is also an important class element to all this. (Cue Monty Python: “There he goes bringing class into it again.” “But that’s what it’s all about!”) For the upper and middling classes, industrialization created significantly more leisure time and (perhaps) an increasing divide between the public and private spheres. While men joined social clubs and spotting groups, women’s circles often met to read and discuss novels, poetry, and diarying. Of course men discussed these things too, but especially with the growth of industry, an increasing middle-class/managerial group, and the professionalization of writers and journalists, business-minded men began to grow separate from the groups and organize to discuss literature. Although women’s social practices changed too, the idea of domestic sphere prevailed well into the 1980s. As a growing number of women entered suburbia and the household economy became increasingly industrialized, many women had more free time. Diary keeping was seen as certain right of passage, especially for women who believed they had joined the middle class. Even if some elements of the cult of domesticity did not last into the late twentieth century, the idea that proper women recorded their thoughts in diaries certainly persisted among certain social circles.

Again, I can only speak to an incredibly Anglo-centric history. My answer does not lend itself across cultures. We need a lot more input if we want to understand diarying and its relationship to gender norms beyond my limited analysis.

TL;DR: Diarying, at least as we know it, is really a product of the Enlightenment, and as such, is wrapped up with emerging conceptions of masculinity and femininity connected to public and private life and expressions of refinement.

Some material to read:

Hayden White, Metahistory (1973) and Content of the Form (1987)

Rebecca Steinitz, Time, Space, and Gender in the Nineteenth-Century British Diary (2011)

Ronald J. Zboray and Mary Saracino Zboray, “Is It a Diary, Commonplace Book, Scrapbook, or Whatchamacallit? Six Years of Exploration in New England's Manuscript Archives,” Libraries & the Cultural Record 44, no. 1 (2009).

Kacy Dowd Tillman, Stripped and Script: Loyalist Women Writers of the American Revolution (2019)