The fact that you follows closely behind I in popularity is probably attributable to its being both subject and object, both singular and plural, and both formal and familiar.
The all-purpose second person is an unusual feature of English, as middle-schoolers realize when they start taking French, Spanish, or especially German, which offers a choice of seven different singular versions of you.
It’s relatively new in our language. In early modern English, beginning in the late fifteenth century, thou, thee and thy were singular forms for the subjective, objective and possessive, and ye, you and your were plural. In the 1500s and 1600s, ye and then the thou / thee / thy forms, faded away, to be replaced by the all-purpose you. But approaches to this second person were interesting in this period of flux.
David Crystal writes in The Cambridge Encyclopedia of English that by Shakespeare’s time, you “was used by people of lower rank or status to those above them (such as ordinary people to nobles, children to parents, servants to masters, nobles to the monarch), and was also the standard way for the upper classes to talk to each other. […] By contrast, thou / thee were used by people of higher rank to those beneath them, and by the lower classes to each other; also in elevated poetic style, in addressing God, and in talking to witches, ghosts and other supernatural beings.”
The Oxford English Dictionary cites a 1675 quotation: “No Man will You God but will use the pronoun Thou to him.”
Needless to say, this ambiguity and variability were gold in the hand of a writer like Shakespeare, and he played with it endlessly, sometimes having a character switch modes of address within a speech to indicate a change in attitude.
Crystal cites Sir Toby Belch’s advice to Sir Andrew Aguecheek, in Twelfth Night, on how to get under the skin of an antagonist: “if thou thou’st him some thrice, it will not be amiss.”
Sir Toby, of course, is himself thou-ing Sir Andrew.
Ben Yagoda (1954–) is an American writer and educator. He has been a professor of journalism and English at the University of Delaware until 2018.
This excerpt from When You Catch an Adjective, Kill It: The Parts of Speech, for Better and/or Worse (Broadway Books, 2007) has been published by DelanceyPlace, “a brief daily email with an excerpt or quote we view as interesting or noteworthy”.