bend: [OE] English band, bind, bond, and bundle are closely allied: all go back to a prehistoric Germanic base *band-. The relationship in meaning was, in the case of bend, more obvious in Old English times, when bendan meant ‘tie up’ as well as ‘curve’ (a sense preserved in the modern English noun bend ‘knot’, as in carrick bend).
The rather strange-seeming meaning development appears to have come about as follows: bend in the sense ‘tie, constrain’ was used for the pulling of bow-strings, with reference to the strain or tension thereby applied to the bow; the natural consequence of this was of course that the bow curved, and hence (although not until the late 13th century) bend came to be used for ‘curve’. => band, bind, bond, bundle
Old English bendan "to bend a bow; confine with a string, fetter," causative of bindan "to bind," from Proto-Germanic base *band- "string, band" (cognates: Old Norse benda "to join, strain, strive, bend"), from PIE root *bhendh- "to bind" (cognates: Gothic bindan, Old High German bintan, Sanskrit badhnati "binds," Lithuanian bendras "partner;" Old Persian bandaka- "subject").
Modern sense (early 14c.) is via notion of bending a bow to string it. Cognate with band, bind, and bond. Related: Bended; bent; bending.