means A small open-topped pastry with a filling of fruit, custard, or jam and no crust on top — though as an adjective it also means sharp or acidic in taste, and figuratively, sharp in speech.

from From Old French 'tarte,' a kind of flat pastry, which passed into Middle English. The adjective 'tart' (sharp-tasting) is a separate, older word from Old English 'teart,' meaning severe or rough. The two meanings sit side by side by accident of sound. The slang use of 'tart' for a woman is a much later development, likely a shortening of 'sweetheart' that soured over time into something disreputable — a journey from endearment to insult.