Ricardo, a reader, wonders why the second person singular pronoun dropped out of English.
In the earliest form of English, the difference between the pronouns thou and ye was one of number. Thou (object form: thee) was singular and ye (object form: you) was plural.
In the 11th century (1066) the French-speaking Normans invaded and conquered England. French became the language of the rich and powerful, while English was chiefly the language of the conquered.
Whenever cultures collide, each side takes something from the other. English speakers adopted the French practice of using the singular second person pronoun to address family members, friends, children, and social inferiors. Ye and You began to be used as a respectful singular form when speaking to superiors. By the 13th century the practice had become common in English.
In time, for political reasons, the descendants of the Norman conquerors abandoned French and adopted the language of the conquered.
By Chaucer’s time (14th century) English was the language of the court. The dialect that Chaucer wrote in, rich in French vocabulary, is the dialect that has become modern English.
So what happened to thou? My theory is that the word had become so offensive because of its use as a class marker that eventually everyone demanded to be addressed by the respectful ye (you). We can see in our own time a process at work that leads to the deliberate disuse of certain words that are seen as being disrespectful.
This line from a 16th century play whose name escapes me illustrates that thou had the power to ruffle feathers:
Dost thou “thou” me, thou dog?!
The speaker is clearly annoyed at having been addressed as “thou.”
Scholars have always tended to defend traditional forms even after popular usage has shifted.
The language of the King James translation of the Bible (1611), for example, is very conservative in its use of pronouns. In Genesis 3:15, God tells the serpent “I will put enmity between thee and the woman.” In Genesis 6:18 Noah is told “…thou shalt come into the ark, thou, and thy sons, and thy wife, and thy sons’ wives with thee.”
Popular usage differed. By the 16th century the forms thou/thee/thy had fallen out of polite use except among the Quakers. That religious group chose to emphasize social equality by dropping you as a respectful singular form and addressing individuals of every class as thou/thee
Ye, the subject form of you, went the way of thou.
Before you triumphed as the all-purpose second person pronoun, ye was the subject form and you was the object form. The two words sounded too much alike to remain separate and the distinction was already being lost in the 16th century.
The distinction is observed in the 1611 translation of Job 12:2:
No doubt but ye are the people, and wisdom shall die with you.
Shakespeare, however, uses both ye and you as objects in this line for Caliban in The Tempest (I, ii 320-324):
A southwest wind blow on ye And blister you all over!
And that, y’all, is the story of how thou lost out to you in English.
(Verification for the information in this article can be found in A.C. Baugh, The History of the English Language.)