mollusk Look up mollusk at Dictionary.com
1783, from Fr. mollusque, from Mod.L. Mollusca, order name, adopted by Linnĉus 1758 from L. mollusca, neut. pl. of molluscus "thin-shelled," from mollis "soft," from PIE base *mel-/*mol-/*ml- "grind." Linnĉus applied the word to a heterogeneous group of invertebrates, not originally including mollusks with shells; the modern scientific use is after a classification proposed 1790s by Fr. naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier (1769-1832).