Note: The origins for certain expressions can be unclear. When that happens, what I'll usually do is this: If there are theories floating around for how a saying originated or where it may have come from, then I'll list one or two of those.
Also, I want to give the reader an idea on how far back in history an expression goes, so on every page, I try to include the oldest written quote of the saying that I can find. Of course, it's possible that older quotes exist and I'm unaware of them. If you know of an older quote, feel free to contact me and let me know.
knowyourphrase.com - Meanings and Origins of Phrases
Being angry about something that happened in the past; holding a grudge.
This common phrase is said to those who remain upset over problems they've experienced in the past.
This phrase goes back to at least the 1800s. A 'chip' can be defined as a piece of timber, or wood. Depending on the amount and size of it, a piece of timber can be quite heavy, and sometimes people carry heavy things on their shoulders. There was apparently a point in time where certain people, who I assume were angry, would place a chip on their shoulder in order to show that they were looking for a fight. With the wood, or 'chip' placed firmly on their shoulder, they would dare others to knock it off. Anyone who wanted to accept the proposed challenge could do so, and then a fight would occur shortly after.
There were newspapers from the 19th century mentioning something along these lines. For example, the Long Island Telegraph newspaper printed on May 20th, 1830, wrote:
"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."
Another example comes from the Onondaga Standard of Syracuse, New York, 1830, wrote:
"'He waylay me', said I, 'the mean sneaking fellow - I am only afraid that he will sue me for damages.
Oh! if I only could get him to knock a chip off my shoulder, and so get round the law, I would give him
one of the soundest thrashings he ever had.'"
* Chell still has a chip on her shoulder over the argument we had yesterday, but hopefully we can move past this soon. I think I will apologize next time I see her!
The Idiom - A Chip On Your Shoulder - With Its Meaning And Origin