1.  A tendon or tendonous tissue. See Tendon. [1913 Webster]

2.  Muscle; nerve. Sir J. Davies. [1913 Webster]

3.  Fig.: That which supplies strength or power. [1913 Webster]
" Money alone is often called the sinews of war." [1913 Webster]
"The portion and sinew of her fortune, her marriage dowry." [1913 Webster]
"The bodies of men, munition, and money, may justly be called the sinews of war." [1913 Webster]

   To knit together, or make strong with, or as with, sinews. Shak. [1913 Webster]
"Wretches, now stuck up for long tortures . . . might, if properly treated, serve to sinew the state in time of danger." [1913 Webster]

sinew, n. & v.
--n.
1 tough fibrous tissue uniting muscle to bone; a tendon.
2 (in pl.) muscles; bodily strength; wiriness.
3 (in pl.) that which forms the strength or framework of a plan, city, organization, etc.
--v.tr. poet. serve as the sinews of; sustain; hold together.

Idiom:
the sinews of war money.

Derivative:
sinewless adj. sinewy adj.

Etymology:
OE sin(e)we f. Gmc

N  strength, power, energy, vigor, force, main force, physical force, brute force, spring, elasticity, tone, tension, tonicity, stoutness, lustihood, stamina, nerve, muscle, sinew, thews and sinews, physique, pith, pithiness, virtility, vitality, athletics, athleticism, gymnastics, feats of strength, adamant, steel, iron, oak, heart of oak, iron grip, grit, bone, athlete, gymnast, acrobat, superman, Atlas, Hercules, Antaeus, Samson, Cyclops, Goliath, tower of strength, giant refreshed, strengthening, invigoration, refreshment, refocillation, dynamics, statics, strong, mighty, vigorous, forcible, hard, adamantine, stout, robust, sturdy, hardy, powerful, potent, puissant, valid, resistless, irresistible, invincible, proof against, impregnable, unconquerable, indomitable, dominating, inextinguishable, unquenchable, incontestable, more than a match for, overpowering, overwhelming, all powerful, all sufficient, sovereign, able-bodied, athletic, Herculean, Cyclopean, Atlantean, muscular, brawny, wiry, well-knit, broad-shouldered, sinewy, strapping, stalwart, gigantic, manly, man-like, manful, masculine, male, virile, unweakened, unallayed, unwithered, unshaken, unworn, unexhausted, in full force, in full swing, in the plenitude of power, stubborn, thick-ribbed, made of iron, deep-rooted, strong as a lion, strong as a horse, strong as an ox, strong as brandy, sound as a roach, in fine feather, in high feather, built like a brick shithouse, like a giant refreshed, strongly, by force, by main force, our withers are unwrung, Blut und Eisen, coelitus mihi vires, du fort au diable, en habiles gens, ex vi termini, flecti non frangi, he that wrestles with us strengthens our nerves an, inflexible in faith invincible in arms.