Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.

WORD ORIGIN

"to relax a bow by unstringing it," mid-13c., from un- (2) + bend (v.). Figurative meaning "to become genial, relax" (1748) has a sense opposite to that of unbending "inflexible, obstinate" (1680s), which does not derive from the bowstringing image.

Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.