Old English bendan "to bend a bow, bring into a curved state; confine with a string, fetter," causative of bindan "to bind," from Proto-Germanic base *band- "string, band" (source also of Old Norse benda "to join, strain, strive, bend"), from PIE root *bhendh- "to bind."
Meaning "curve or make crooked" (early 14c.) is via the notion of bending a bow to string it. Intransitive sense of "become curved or crooked" is from late 14c., that of "incline, turn from the straight line" is from 1510s. Figurative meaning "bow, be submissive" is from c. 1400. Cognate with band, bind, bond, and Bund. Related: Bended; bent; bending.
1590s, "a bending or curving;" c. 1600, "thing of bent shape, part that is bent;" from bend (v.). The earliest sense is "act of drawing a bow" (mid-15c.). Old English bend (n.) meant "bond, chain, fetter; band, ribbon," but it survives only in nautical use in this form, the other senses having gone to band (n.1). The bends "decompression pain" first attested 1894.
"broad diagonal band in a coat-of-arms, etc.," mid-14c., from earlier sense of "thin, flat strap for wrapping round," from Old English bend "fetter, shackle, chain," from PIE *bhendh- "to bind" (see bend (v.)). Probably in part also from Old French bende (Modern French bande) and Medieval Latin benda, both from Germanic. Ordinarily running from the right top to the left bottom; the bend sinister runs along the other diagonal.