I know it’s a very British phrase, but “to shop a person” in the sense of “turning them in to the police” has always been of interest to me. I mean how do you get from “shops” and “shopping” in the retail sense to telling on someone / pointing the police in their direction?
Well, I was rewarded for my curiosity! Apparently, at one time, to be imprisoned was to be shopped. Not entirely clear why, but somewhere that shifted into getting someone put in prison being “shopping them”.