Chip on one's shoulder

[Robinbuildsbears]

I've always assumed that the metaphor was akin to a chip in one's tooth, but I've mostly heard people say things like "want some salt for that chip on your shoulder", as if it's referring to the french fries type of chip. Which way is the saying intended to be about?

From Wiki:

This idiom traces its roots back to a custom that was known in North America since the early 19th century. The New York newspaper Long Island Telegraph reported on 20 May 1830 "when two churlish boys were determined to fight, a chip [of wood] would be placed on the shoulder of one, and the other demanded to knock it off at his peril".

Asking if someone wants salt on their chip is nothing to do with the actual (imagined!) chip, just drawing attention - in a sarcastic way - to how someone is behaving/speaking.

I didn't KNOW, but my instinct would have been that it was a chip of wood.

I thought it was like being a damaged statue.

It's a chip of wood, but not a small piece.