Shirty

  
Someone asked me the other day what was the origin of the word shirty. This is an informal British expression and means ill-tempered; cranky; irritated, or annoyed.

It dates back at least to 1846 and "To get a person's shirt out" has meant to cause someone to lose his or her temper since that period as well. "Keep your shirt on," meaning to calm down, dates to the same period. In all cases the reference is to loosening or completely removing one's shirt in preparation for a fight.