A tonsillolith (also called tonsil stone, tonsil rock, tonsillar debris, tonsillar pearl, zot, pebbles, bad breath bead, smelly jelly, stinky seed, throat poo, lung butter, or calculus of the tonsil) is a piece (or more commonly, a cluster) of calcareous matter which forms in the rear of the mouth, in the crevasses (called tonsillar crypts) of the palatine tonsils (which are what most people commonly refer to as simply tonsils)