In early England, one man would challenge another to a duel by slapping his face with a glove.
The challenge was a serious matter of honor, and if the slapped man did not accept it, he would be branded a coward.
Having a chip on your shoulder was kind of an early Wild West equivalent of the glove slap, though generally less mortal in nature.
Boys and men would place a woodchip on their shoulder, challenging anyone who dared knock it off to a fistfight.
So, if a man had a “chip on his shoulder,” he was clearly in an aggressive mood and spoiling for a fight.
The custom was first documented in North America by the Long Island Telegraph, a New York newspaper, on May 20, 1830.
The expression “A chip on the shoulder” comes from the ancient right of shipwrights within the Royal Navy Dockyards to take home a daily allowance of timber.
As a result of abuse, shipwrights were ordered to carry their bundles under their arms instead of on their shoulders to limit the amount they could take.
Angry shipwrights showed their defiance by carrying their chips on their shoulders.
And the rest is history.