thigh (n.) Look up thigh at
Old English þeoh, þeh, from Proto-Germanic *theuham (source also of Old Frisian thiach, Old Dutch thio, Dutch dij, Old Norse þjo, Old High German dioh), probably literally "the thick or fat part of the leg," from PIE *teuk- from root *teue- (2) "to swell" (source also of Lithuanian taukas, Old Church Slavonic tuku, Russian tuku "fat of animals;" Lithuanian tukti "to become fat;" Avestan tuma "fat;" Greek tylos "callus, lump," tymbos "burial mound, grave, tomb;" Old Irish ton "rump;" Latin tumere "to swell," tumulus "raised heap of earth," tumidus "swollen;"tumor "a swelling;" Middle Irish tomm "a small hill," Welsh tom "mound").