English

insinew

From in- + sinew.

Formed from in- + sinew

Proto-Indo-European *h₁én ‘in’

Proto-Germanic *in ‘into’

English in-

Proto-Indo-European *(s)neh₁- ‘to twist threads, spin, weave’

…

Proto-Germanic *sinwō ‘cord, tendon, sinew’

Proto-West Germanic *sinu

Old English sinu ‘tendon, sinew’

Middle English synwe ‘tendon’

English sinew

Today it means

verb To strengthen with, or as if with, sinews; to innerve; to invigorate.

Language periods are conventional ranges, not dates for this word.