Most European languages possess what linguists call "The T-V Distinction."

That is, they have a formal word for "you" and then a more informal - or offensively condescending - "you" as well.

German has "du" between friends, and "sie" if you're being more formal.

(Read on)

French has "vous" (formal) and "tu".

If a person in a position of power, who should be spoken to with a "vous" (French) or a "sie" (German), uses an informal "tu" or "du" with a person of inferior rank, they are being deliberately offensive by being overfamiliar.

It's akin to a policeman saying "Well, well, well. What have we here, my lovely?" when they're trying to intimidate you.

Now, English doesn't have these two forms of "you" - but we used to.

In my plays, "you" is formal, but "thou" is used for intimates, and to be offensive.

Consider the opening passage of Julius Caesar, where this high-ranking tribune is addressing common folk:

MARULLUS
But what trade art thou? answer me directly... What trade, thou knave? thou naughty knave, what trade?

He is addressing a working-class cobbler. Note the "thou".

And this wonderful line from that hymn to love, Romeo and Juliet:

My bounty is as boundless as the sea,
My love as deep; the more I give to thee,
The more I have, for both are infinite.

Had she written "you" instead of "thee", it would have seemed absurd.

And the famous opening lines from the sonnet:

"Shall I compare thee to a summer's day?
Thou art more lovely and more temperate..."

So, there you go. T-V Distinction. Now you know.