sinewy (adj.)

"cord or tendon of the body," connecting a muscle to a bone or other body part, Middle English sineu, from Old English seonowe, oblique form of nominative sionu "sinew," from Proto-Germanic *sinwō (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").

adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.