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. 1200, "to link or connect, as one thing with another," from Old French copler "to couple, join together," from cople (see couple (n.)). Meaning "unite in marriage" is from mid-14c.; that of "embrace sexually, copulate" is from c. 1400. Related: Coupled; coupling.
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<a href="https://www.etymonline.com/word/uncouple">Etymology of uncouple by etymonline</a>
Harper, D. (n.d.). Etymology of uncouple. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/uncouple