1570s, originally a weasel-like animal in Egypt, Latinized from Greek ikhneumon, literally "searcher, tracker," perhaps because it hunts crocodile eggs, from ikhneuein "hunt for, track," from ikhnos "a track, footstep, trace, clue," of unknown origin. Used by Aristotle for a species of wasp that hunts spiders (a sense in English from 1650s).