sinew

Etymology

of the calf to the calcaneus or heel bone]] From Middle English synwe, synewe (“tendon; ligament or other connective tissue; muscle; nerve; leaf vein”), from Old English sinu (“tendon, sinew; nerve”), from Proto-West Germanic *sinu, from Proto-Germanic *sinwō, *senawō (“sinew”), from Proto-Indo-European *snḗh₁wr̥ (“tendon, sinew”), from *(s)neh₁- (“to twist (threads), spin, weave”). The word is cognate with sinnow (“sinew”), Scots senon, sinnon, Saterland Frisian Siene (“sinew”), West Frisian senuw, sine (“sinew; nerve”), Dutch zenuw (“nerve, sinew”), German Sehne (“tendon, sinew; cord”), Icelandic sin (“tendon”), Swedish sena (“sinew”), Avestan 𐬯𐬥𐬁𐬎𐬎𐬀𐬭 (snāuuar, “tendon, sinew”), Ancient Greek νεῦρον (neûron, “tendon; nerve; cord”), Latin nervus (“tendon, sinew; nerve”), Sanskrit स्नावन् (snāván, “sinew, tendon; muscle”), Tocharian B ṣñor (“sinew”). Doublet of nerve and neuron.

noun

1. (anatomy) A cord or tendon of the body.
2. A cord or string, particularly (music) as of a musical instrument.
3. (figurative) Muscular power, muscle; nerve, nervous energy; vigor, vigorous strength.
4. (figurative, often in the plural) That which gives strength or in which strength consists; a supporting factor or member; mainstay.
   The Bodies of Men, Munition, and Mony may justly be called the ſinews of War, yet of them the two firſt are more neceſſary, for Men and Arms have means to find Mony and Meate: but Mony and Meate cannot ſo eaſily find Soldiers and ſwords. 1658, Walter Raleigh, “A Collection of Political Observations (Confirmed by Reason and Experience) Advertising Princes, Statesmen, and Private Persons how to Demean Themselves in All Fortunes and Events”, in The Cabinet-Council: Containing the Cheif Arts of Empire, and Mysteries of State;[…], London: Published by John Milton; printed by Tho[mas] Newcomb for Tho[mas] Johnson[…], →OCLC, page 101
5. (anatomy, obsolete) A nerve.

verb

1. (transitive) To knit together or make strong with, or as if with, sinews.