means A soft-bodied invertebrate—like a snail, clam, squid, or octopus—usually built around a muscular foot and often protected by a shell.

from From Latin 'molluscus,' meaning 'soft' or 'thin-shelled,' itself from 'mollis,' 'soft' (a cousin of words like 'mollify' and 'emollient'). Naturalists borrowed it to name these tender-bodied creatures, the squishiness being the whole point: a mollusk is, etymologically, just 'the soft one.'