unscramble 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)).

1580s (intransitive), "make one's way by clambering, etc., struggle or wriggle along," also "strive with others or jostle and grasp rudely for a share or for mastery;" a word of obscure origin, perhaps a nasalized variant of scrabble (v.) "to struggle; to scrape quickly." OED points to dialectal scramb "pull together with the hands," a variant of scramp, which is probably a nasalized form of scrape.

Mrs. Goddard was the mistress of a school, ... a real, honest, old fashioned boarding-school, where a reasonable quantity of accomplishments were sold at a reasonable price, and where girls might be sent to be out of the way, and scramble themselves into a little education, without any danger of coming back prodigies. [Jane Austen, "Emma"]

The transitive sense of "to stir or toss together randomly, cause to move confusedly" is from 1822. The transitive sense, in reference to radio signals, telephone voices, etc., "to make unintelligible," is attested from 1927, hence generally "to jumble, muddle." In U.S. football, in reference to a quarterback avoiding tacklers, by 1964. Related: Scrambled; scrambling. Scrambled eggs, broken into a pan, mixed with butter, salt, pepper, etc., and cooked slowly,is by 1843.