Etymology
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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.
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disclose (v.)

late 14c., disclosen, "to uncover and expose to view, open to the knowledge of others," from Old French desclos "open, exposed, plain, explicit," past participle of desclore (Modern French déclore) "open, break open, unlock, reveal," from des- "opposite of" (see dis-) + clore "to close" (see close (v.)). Related: Disclosed; disclosing.

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solve (v.)
late 14c., "to disperse, dissipate, loosen," from Latin solvere "to loosen, dissolve; untie, release, detach; depart; unlock; scatter; dismiss; accomplish, fulfill; explain; remove," from PIE *se-lu-, from reflexive pronoun *s(w)e- (see idiom) + root *leu- "to loosen, divide, cut apart." The meaning "explain, answer" is attested from 1530s; for sense evolution, see solution. Mathematical use is attested from 1737. Related: Solved; solving.
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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)).
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