ichneumon

英 [ɪk'njuːmən] 美[ɪk'njʊmən]

ichneumon: ichneumon: [16] Ichneumon comes from a Greek word which meant literally ‘tracker’. This was ikhneúmōn, a derivative of íkhnos ‘track, footstep’. Aristotle used it as the name for a species of wasp that hunted spiders, and it was adopted into English in this sense for the ichneumon fly, a wasplike insect with parasitic larvae, in the 17th century. Its original English application, however, was to a variety of African mongoose which ‘tracks down’ or hunts out crocodile eggs.
ichneumon (n.): 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).