sinew

The word 'sinew' descends from Old English 'sinu' or 'seono,' meaning a tendon — the tough, fibrous band of connective tissue that attaches muscle to bone.‍​‌​‍​‌​‍​‍​‌​‌​‍​‍​‍​‌​‌​‍​‍​‌​‌​‍​‌​‍​‍​‌​‌​‌​‌​‌​‌​‍​‌​‍​‌​‍ The Old English form comes from Proto-Germanic *sinwō, with cognates in German 'Sehne' (sinew, tendon, bowstring), Old Norse 'sin' (sinew), and Dutch 'zenuw' (nerve — a telling semantic shift). The Proto-Germanic word derives from PIE *sey- (to bind, to tie), making 'sinew' literally 'the binder' — the tissue that binds the muscular system to the skeletal system.

The semantic history of 'sinew' reveals a fundamental confusion in pre-modern anatomy. Before the development of precise dissection and microscopy, Europeans did not clearly distinguish between tendons (which connect muscle to bone), ligaments (which connect bone to bone), and nerves (which transmit signals). All three were seen as varieties of the same thing: tough, cord-like structures within the body. Latin 'nervus' meant all three — sinew, nerve, and bowstring. Greek 'neûron' (νεῦρον) similarly meant sinew and nerve interchangeably. This is why English 'nerve' once meant 'sinew' (a 'nervous' arm was a muscular one), and why German 'Sehne' means both 'sinew' and 'the string of a bow,' and Dutch 'zenuw' means 'nerve' — all reflexes of the same original confusion.

The phrase 'the sinews of war' — meaning the money, resources, and logistics needed to sustain a military campaign — has a distinguished literary pedigree. Cicero wrote 'nervos belli, pecuniam infinitam' (the sinews of war, unlimited money) in the first century BCE. Francis Bacon echoed it in English. The metaphor treats war as a body whose sinews (strength, structural support) are financial resources. The phrase remains current: 'the sinews of power' and 'the sinews of government' are common variations.

Sinew itself — actual animal tendon — was one of the most important materials in pre-industrial technology. Bowstrings were made from sinew (the back sinew of deer was preferred). Sinew was used as thread for sewing leather and hides. In archery, 'sinew-backed' bows — composite bows with a layer of sinew glued to the back — were used across Central and East Asia, the Arctic, and parts of North America. The elasticity of dried sinew made it superior to plant fibers for storing and releasing energy in a bow.

The adjective 'sinewy' means lean and muscular, with visible tendons — the physique of a laborer or athlete. It has been used figuratively since the sixteenth century to describe prose or argument that is lean, tough, and strong: 'sinewy prose' has no fat, no excess, only functional strength. Ben Jonson praised Shakespeare for 'sinewy' language.

In the Bible, sinews carry particular symbolic weight. The vision of the Valley of Dry Bones in Ezekiel 37 describes the resurrection of Israel through the image of sinews forming on skeletons: 'and the sinews and the flesh came up upon them, and the skin covered them above.' The passage uses the physical reconstruction of a body — bones, then sinews, then flesh, then breath — as a metaphor for national restoration.

Modern anatomy has replaced 'sinew' with 'tendon' in technical usage. 'Tendon' entered English from medieval Latin 'tendō' (I stretch), from Latin 'tendere' (to stretch), from PIE *ten- (to stretch). The Achilles tendon — the body's largest and strongest tendon — connects the calf muscles to the heel bone and is crucial for walking, running, and jumping. Its name commemorates the Greek hero Achilles, whose only vulnerable point was, according to myth, his heel.