so i thought maybe "spoiling for a fight" was some nautical thing, like putting up a weird little sail so you could maneuver better during close action
but according to some internets the first printed use was in 1858
it's an Americanism that seems to mean you'll "spoil for want of a fight", like a poorly treated or stored crop
this is sort of cute
you want that fight and you're about to turn into a bad vegetable if you don't get it