Chip on his shoulder
Chip on his shoulder : Phrases
Someone who is sulky, aggressive and moody
Henrietta had a chip on her shoulder for being turned down for another promotion.
The phrase is based on an American schoolboy custom, about 200 years old. When two boys were arguing and itching for a fight then one would place an actual chip of wood on his shoulder and challenge the other to knock it off. If the challenge was taken up, then the proper fight started.