[Necrosis]

Chat and/or Chatting

British soldiers in WW1 were consumed /w body lice in the trenches. They called these lice "chats", and would sit together picking them off one another. Thus the term "chatting".

[dj_stick]

mmm there was another thread like this not too long ago

some of these origins are really interesting

[Ðamage™]

Chip on your shoulder:

When two churlish boys were determined to fight, a chip would be placed on the shoulder of one, and the other demanded to knock it off at his peril”. It seems to have been a challenge in the same spirit as a medieval knight throwing down his gauntlet. If your opponent picked up the glove, or knocked the chip of wood off your shoulder, the challenge was accepted and the fight was on. Later it came to suggest somebody who shows a belligerent attitude, acting as though he were spoiling for a fight; the chip was figurative, but the idea was the same.

[Drakon]

Wow. Interesting stuff