early 14c., "to undo" (a bandage, wrapping, etc.), from un- (2) "opposite of" + wind (v.1). Similar formation in Old English unwindan "unveil, uncover," Dutch ontwinden, Old High German intwindan. Reflexive sense is recorded from 1740; figurative sense of "to release oneself from tensions, to relax" is by 1938. Related: Unwound; unwinding.
