the.com/tartar

means The hardened, crusty mineral deposit that forms on teeth when plaque isn't removed and calcifies over time.

from The word traveled a winding road: 'tartar' originally named a crusty crystalline deposit (potassium bitartrate) that forms inside wine barrels during fermentation — chemists called this 'tartar' from medieval Latin 'tartarum.' Because dental tartar looked and behaved like that same hard, crusty residue, the name was borrowed straight over to teeth. It's unrelated to the Tartars (Central Asian peoples) or to tartar sauce, despite the shared spelling — those are separate historical tangles, not cousins.