lizard: [14] Lizard goes back to Latin lacertus or lacerta, words of unknown origin. It reached English via Old French lesard. The Latin word was used for ‘muscle’ as well as ‘lizard’, perhaps because the ripple of a muscle beneath the skin reminded people of a lizard’s movement (an exactly parallel development links mouse and muscle). And in heavily disguised form, owing to a detour via Arabic, alligator is the same word. => alligator
