What does i know you of old mean in shakespeare?

"I know you of old" in Shakespearean English means that the speaker has known the person they are speaking to for a long time. It is a way of saying that they are familiar with the other person's character, personality, and history.

For example, in Romeo and Juliet, Mercutio says to Romeo, "I know you of old." In this context, Mercutio means that he knows Romeo very well and knows that he is the type of person who is quick to get into fights.