In Shakespearean times, the poor people (groundlings) were known to be lowkey stupid, and drool in awe when excited. Because the groundlings were placed right in front of the stage and so damn slobbery, the drool would drip onto the stage. So if the actor was slaying, the groundlings would drool, resulting in the actor's inevitable slip and bone fracture.
They are loving your performance so much! Hopefully they'll drool enough that you break a leg!
When two or more parties are fighting in one way or another, and an external party comes in to settle the situation - or make it worse. May be repeated for greater effect, or if said parties were too heated up in the argument to listen.
"hater ass fish fuck you"
"broke bitch fuck your land"
"Break it up!"