unseal (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. 1200, selen, "to fasten (a letter, etc.) with or as with a seal, close up with a seal, press a seal on wax," also "place a seal on (a document)," also figurative, "to join together," from seal (n.1) or else from Old French seeler, sealer.

Hence "to conclude, ratify, render official or binding" by affixing seals to it (late 15c.). In reference to jars or other containers, "to close up with wax, lead, cement, etc.," attested from 1660s, from the notion of wax seals on envelopes. In reference to the actions of wood-coatings, "render impervious," by 1940. Related: Sealed; sealing.

Sealing-wax, "soft substance prepared for receiving the impression of a seal," is attested from c. 1300. To seal (one's) lips "be silent" is by 1782. To seal (one's) fate (1799) "decide irrevocably" perhaps reflects the notion of a seal on a warrant of execution.