unsheathe (v.)

prefix of reversal, deprivation, or removal (as in unhand, undo, unbutton), Old English on-, un-, from Proto-Germanic *andi- (source also of Old Saxon ant-, Old Norse and-, Dutch ont-, Old High German ant-, German ent-, Gothic and- "against"), from PIE *anti "facing opposite, near, in front of, before, against" (from PIE root *ant- "front, forehead," with derivatives meaning "in front of, before").

More or less confused with un- (1) through similarity in the notions of "negation" and "reversal;" an adjective such as unlocked might represent "not locked" (un- (1)) or the past tense of unlock (un- (2)).

c. 1400, shethen, "furnish (a sword, etc.) with a sheath" (a sense now obsolete), from sheath (q.v.), or from Old English *sceaþian (implied in unsceaþian). The meaning "put (a sword, etc.) in a sheath" is attested from early 15c. The general sense of "cover over, encase" is by 1630s. Related: Sheathed; sheathing.