When you have a chip on your shoulder, it means you’re in a foul mood because of some injustice, imagined or not, you believe another person or group of people have directed against you. It also implies that you can easily become upset. But what exactly is the origin of this popular expression?

To start out with, just in case you’re uncertain, the ‘chip’ being referred to is a hunk of wood, not a chunk of delicious chocolate, or a salty potato chip.

The origins of this phrase date back to 18th century British Naval shipyards, when shipwrights were allowed to carry home excess timber, or wood ‘chips,’ for their personal use. Well, some of the workers took advantage of this special privilege and ended up toting off more than their fair share.

The rules subsequently changed, and the men were only allowed to carry wood home under one arm, instead of the heavier loads they were accustomed to hauling on their shoulders. It goes without saying that the shipwrights were less than pleased with the new restrictions, and many still tried to carry their chips home on their shoulders.

In North America, the expression came into common usage in the 19th century. When a boy, or a man, was spoiling for a fight, he would walk around town with a literal chip of wood on his shoulder, as a kind of advertisement. The hopeful combatant would then dare someone to knock the chip off. Anyone who took him up on his offer would have to suffer the violent consequences.

These days the chips are imaginary, but the sore feelings and bad tempers people experience when they think they have been slighted are still very real.