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

WORD ORIGIN

Old English unbindan, "to free from binding," from un- (2) + bind (v.). Cf. German entbinden, Dutch ontbinden. Literal and figurative senses both present in Old English.

Unbound is from Old English unbunden, in literal sense. Figurative sense first attested late 14c.; of books from 1540s.