Thigh

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Old English thēh, thēoh, thīoh, of Germanic origin; related to Dutch dij .

wiktionary

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

etymonline

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thigh (n.)

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- "to swell."