Many languages have a formal and informal "you". The french have "Vous" vs. "Tu", the germans "Sie" vs. "Du", the italians "Voi" and "Tu", and so on.
Well it turns out English does have a formal "you", and I've used it 3 times already: It's "You" :)
We also had (or have, though the dictionary considers it archaic) an informal version: "Thou" was the common verb, until the more formal "Ye", later "You" was brought into English toward the end of the time that French was the language of the ruling class to align with the Vous/Tu segregation.
Then, quite quickly in the early 17th Century it fell out of use in recieved English. This is because it was too easy to offend by "thou-ing" someone when one shouldn't.
It lives, party, in the North though, where "Thee" is still commonly heard, and it is still easy to cause offence. As it's said in Lancashire: "Don't thee me, thee; I's you to thee!"