What is "jacking my jaw"

[leftyladyfrommo]

I hear people say that when they are irritated and I think it sounds dumb. Just what is jacking of the jaw? Couldn't they just say "it pisses me off" like normal people.

[Jamastiene]

1. There was this guy named Jack, you see...

Uh...er...I haven't a clue.

There was once a great boxer named Jack Johnson who knocked somebody's jaw off and knocked half the guy's teeth out at the gums one time. Feathers everywhere.

It might have originated there, but that's only a guess.

[Orrex]

2. Mastication is nothing to be ashamed of

In fact, I'm going to do it right now.

[Lady Effingbroke]

3. Talking too much and not saying enough.