potshot: [19] A potshot was originally a shot taken at an animal or bird simply in order to kill it for food – in order to get it into the ‘pot’, in other words – rather than in accordance with the strict code and precise techniques of shooting as a ‘sport’. Indeed to begin with it was distinctly a contemptuous term among the hunting and shooting fraternity. But gradually it broadened out in meaning to any ‘casually aimed shot’. [potshot etymology, potshot origin, 英语词源]
also pot-shot, 1836, "shot taken at animal simply to 'get it in the pot,' not for sport or marksmanship;" from pot (n.1) + shot (n.). Extended sense of "opportunistic criticism" first recorded 1926. Compare pot-hunter "one who shoots whatever he finds; one who kills for food not for sport."