I saw your post about neopronouns, so please explain: thou
(Btw, no need for this to be concise or anything. You just seem to really enjoy this subject so I wanted to give you an easy way to ramble. I love seeing people talk about the things they love!)
All (bad) jokes aside, the linguistic timeline of 'thou'—or, more accurately, thou/thee/thy in the modern form of identifying pronouns—is one of my favorites I've ever looked into. I find it so fascinating. Thanks for the ask!
To best understand this, I think it'll be fun to make a timeline. So, here we go:
We're just getting started.
When modern speakers hear 'thou', we mainly associate it with religious texts or Shakespeare, which is understandable—the usage of 'thou' dates far back.
'Thou' was a singular pronoun, derived from Proto-Germanic, appearing as 'þu' (thu) in Old English (which, for the record, was over a thousand years ago—long before Shakespeare—and used between the years 450-1150). The fact that it was a singular pronoun is the important bit. Today, we see 'you' as being numerically ambiguous; we could be referring to a singular person, or many people, but in older forms of English the pronoun to refer to a singular person was for 'thou', leaving 'you' as a plural.
Then, as French continued to influence English, turning it to the much more readable Middle English (the language of Chaucer, for context), 'thou' was gradually pushed to the sidelines as the plural 'ye' and 'you' expanded to be used as a singular, too.
French's influence made the English 'you' the equivalent of the French 'vous': it is now formal—what you would use to address someone of high or equal social standing. In turn, 'thou' declined (in a process attributed to semantic derogation) to an informal pronoun used to address someone you were intimate with or, most notably, someone beneath you in the social rankings.
Here's where things start to get bumpy.
In the mid-1600s, in comes George Fox who, in my words, would be described as a filthy prescriptivist. He was the founder of the Quakers, and a large part of early Quaker rhetoric was to avoid class distinction—something I could certainly get behind. Quaker speech, therefore, consciously avoided 'you', opting to use the more neutral thee/thou for everyone regardless of social standing. This extended to them sometimes getting into trouble for refusing to call judges 'your honour', and so forth. Thee/thou became associated with Quaker speech, and not many people liked the Quakers. However, this isn't the biggest impact on the usage—far from it, in fact.
The biggest reason, I believe, that 'thou' lost its popularity is because of developments in society—most notably travel and the industrial revolution, as well as the growing merchant class in the 17th century, which was when this pronoun really hit a decline. People stopped using 'thou' as often because it became harder to judge the class of whom you were speaking with. Social mobility disrupted the otherwise clear and stagnant order of British society. It would be a terrible insult to call someone above you 'thou' on accident, and so you would default to 'you'.
In fact, in Early and Late Modern English, 'thou' became an insult. Perhaps in one of the more surprising turns from something that was once a simple pronoun, to 'thou' someone (morphed into a verb) would insult them. As more people used the pronoun as a method of insulting others, it was favoured even less.
Rolling back to George Fox, a famous line of his goes as follows: "We were often beset and abused, and sometimes in danger of our lives for using these words to some proud men, who would say, 'What! You ill-bred clown, do you thou me?'"
From a simple, singular second-person pronoun, to a token of informality, to an insult, 'thou' has definitely had a ride. And, with its current association with religion, poetry, and the old classics, I earnestly hope it doesn't stop rolling.
