chelydre

From Middle English chelidre, chelyder, chelydre, from Old French chelidre, chelydre, from Latin chelȳdrus (“fetid water serpent”), from Ancient Greek χέλυδρος (khéludros, “amphibious serpent”), from χέλυς (khélus, “tortoise”) + ὕδρος (húdros, “water serpent”). Cognate of French chélydre.

来源：wiktionary