Thou and You

Once upon a time, you used to be the plural form of thou. Then the language changed and you became the formal way of addressing a superior. For some reason, thou stopped being used. The only place it shows up is in the King James Bible and some ancient text that is still read (Chaucer, Shakespeare, etc). These days, because of association with the Bible, thou has come to take on connotations of respect, while you is the egalitarian second person pronoun. Interesting how they flipped positions.