From Middle English thigh, thegh, thiȝ, theȝhe, þigh, þyȝh, from Old English þēoh, þīoh, from Proto-West Germanic *þeuh, from Proto-Germanic *þeuhą, from Proto-Indo-European *tewk-. See also West Frisian tsjea, Dutch dij, Middle High German diech, Icelandic þjó; also Irish tóin (“hind, rump”), Lithuanian táukas (“fat”), Russian тук (tuk, “animal fat”).