the.com/stirrer

means Someone who deliberately provokes conflict or gossip, nudging a pot of trouble without ever appearing to touch it themselves.

from Literally, a stirrer is just one who stirs — from Old English 'styrian,' meaning to move, agitate, or rouse, a very old Germanic verb related to words for stirring up motion generally. The leap from 'one who stirs porridge' to 'one who stirs up trouble' is a natural metaphor: agitating a pot and agitating people look remarkably similar from the outside, and English speakers have long used 'stir up' for inciting unrest. The slang sense of 'stirrer' as a deliberate troublemaker or gossip-monger is a more modern, informal extension — especially common in British and Australian English — of that same old image of churning something that was sitting still.