Unlock

wiktionary

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From Middle English unloken, unlouken, onlouken, from Old English onlūcan(“to unlock”), equivalent to un- +‎ lock. Cognate with Dutch ontluiken(“to unlock”).

etymonline

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unlock (v.)

c. 1400, from un- (2) "reverse, opposite of" + lock (v.). Figurative sense is attested from 1530s. Old English had unlucan "to unlock, open." Related: Unlocked; unlocking.