sinew (n.) Look up sinew at Dictionary.com
Old English seonowe, oblique form of nominative sionu "sinew," from Proto-Germanic *senawo (source also of Old Saxon sinewa, Old Norse sina, Old Frisian sine, Middle Dutch senuwe, Dutch zenuw, Old High German senawa, German Sehne), from PIE root *sai- "to tie, bind" (source also of Sanskrit snavah "sinew," syati, sinati "to bind;" Avestan snavar, Irish sin "chain;" Hittite ishai-/ishi- "to bind").