A tongue reaching out of an open mouth 口, the forked upper strokes marking its tip. Every character about speaking, tasting and licking keeps it: 话 (speech), 甜 (sweet, tongue plus sweetness), 舔 (to lick).
舌头 is the tongue, and like in English it stands for speech itself: 口舌 means a quarrel, and 七嘴八舌 ('seven mouths, eight tongues') is everyone talking at once. 舌战 — a tongue battle — is a debate fought hard.
A TONGUE sticking out of a mouth — the mouth 口 is right there at the bottom.
甜 (sweet) is a tongue 舌 next to 甘 (sweetness) — the taste is written as the organ that tastes it.