the.com/sweet tooth

means A strong, persistent fondness for sugary foods — craving cake and candy over anything savory.

from English has paired body parts with appetites since at least the 1300s, and 'sweet tooth' is one of the oldest survivors — originally used more broadly for a fondness for delicate or luxurious things, not just sugar. By the 1600s it had narrowed to mean exactly what it does now: a particular weakness for sweets. The 'tooth' isn't random — teeth were long used as stand-ins for taste and appetite in English (an old phrase, 'to have a tooth for' something, meant simply to have a liking for it), so the sweetness just stuck to the most literal tool for tasting it.