get someone's shirt out

A dated British slang phrase meaning to make someone angry or irritate them to the point of agitation — referencing the image of someone getting so worked up that their shirt gets untucked from the physical agitation of their anger. It's the kind of colorful expression that was once common in informal British speech but has largely been replaced by more direct language. Still, it captures that specific kind of provocation that pushes someone past mild annoyance into genuine, visible irritation.