clam

Clam comes from Middle English clam, meaning "pincers" or "vice," which traces back to Old English clam, meaning "bond, fetter, grip, grasp," and further back to Proto-West Germanic *klammjan, "to press or squeeze together."

From a word about gripping and clamping, clam picked up looser, figurative senses over time — slang for a dollar (possibly alluding to wampum) and, oddly, slang for a Scientologist, tied to the belief that souls once lived inside clams.

There's a second, separate root: Middle English clammen ("to smear, bedaub"), from Old English clǣman, which gives us clammy — so "clam" the shellfish grip-word and "clammy" the damp-sticky word share sound but not ancestry.