Final question 6

Explain the use of “you” and “thou” in Early Modern English. What lead to the disappearance of “thou”? What other forms of politeness / formality appeared or disappeared at this time period?

The fate of the second person pronouns [i.e. you and thou and thee] in the history of English. This story illustrates the interactionof morphological change and social factors. The fact that personal pronouns exist in most of the world's known languages has persuaded linguists that pronominal reference to speaker, addressee and a third person [i.e. he, she, it, they] is a universal feature of human language. This statement suggests that the system of pronominal reference is fundamentally stable. Now while this is likely to be the case, it is also true that the forms that fill the pronominal system have been involved in tremendous changes in the history of English. Since Old English, phonological (i.e. sound) change combined with morphological levelling (i.e. the loss of formal distinction marked in inflection) has wrought considerable change in the shape and sound of the pronoun system as a whole.

By the beginning of the sixteenth century, the system was becoming unstable, increasingly vulnerable to pragmatically subtle manipulation. In addition to pragmatic factors, the choice of pronoun was also subject to a degree of grammatical conditioning, so that thou seems to have been favoured as the subject of auxiliaries (can, may, shall, will) while you was preferred with lexical verbs (want, think, do, prepare

you thou
address to social superiors <-----> address to social inferiors
address to social equals <-----> address of social equals
(upper class) (lower class)
address in public <-----> address in private
formal or neutral address <-----> familiar or intimate address
respect, admiration <-----> contempt, scorn

http://www2.nau.edu/~eng121-c/politenessin%20AME.htm
In Modern English we use the word "you" as both the singular and the plural form. InOld English, thou was used for addressing one person; ye for more than one. You was around then, and while thou and ye were used as a subject of a clause, you was used as the object. By the time of Early Modern English, the distinction between subject and object uses of ye and you had virtually disappeared, and you became the norm in all grammatical functions and social situations. Ye had become old-fashioned and so, when we see it in the Authorised Bible ('Oh ye of little faith') we are seeing that, in spite of the fact that you may think you understand the language in the Bible better than you do Shakespeare, Shakespeare is more modern!
By Shakespeare's time in Early Modern English you was being used for both singular and plural, but in the singular it also had a role as an alternative to thou and thee . You was used by people of lower status to those above them (such as ordinary people to nobles, children to parents, servants to masters), and was also the formal way for the upper classes to talk to each other. By contrast, thou and thee were used by people of higher rank to those beneath them, and by the lower classes to each other; also, strangely enough, in addressing God, and in talking to witches, ghosts, and other supernatural beings. As a refection of the higher status of males in the male/female context a husband might address his wife as thou , and she might reply respectfully with you .

The use of thou and you also had an emotional dimension. Thou commonly expressed special intimacy or affection; you , formality, politeness, and distance. That form is still used in French today in the use of vous and tu . Thou might also be used by an inferior to a superior, to express such feelings as anger and contempt or to be insulting and this is one of the areas where Shakespeare is able to get extra levels of meaning by showing disrespect by one character for another's status. The use of thou to a person of equal rank could be used as an insult. Sir Toby Belch advises Sir Andrew Aguecheek on how to write a challenge to the Count's youth, Viola: 'if thou thou'st him some thrice, it shall not be amiss' (Twelfth Night).
Shakespeare was acutely aware of the way the Early Modern English language that he grew up with was changing and it is yet another way that he was able to create the levels of meaning that made him such an enduring writer. When students take the trouble to understand the use of the thees and thous they are able to appreciate the additional meaning rather than seeing them as a difficulty.

http://www.nosweatshakespeare.com/resources/shakespeare-early-middle-english.htm