1540s, from un- (2) "opposite of" + glue (v.). Related: Unglued; ungluing. Unglued in figurative sense is recorded from 1922.
Entries linking to unglue
un- 2
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)).
glue v.
"join or fasten with glue," late 14c., from Old French gluer, gluier "smear with glue; join together," from glu "glue, birdlime" (see glue (n.)). Related: Glued; gluing.