Entries linking to undisguised
prefix of negation, Old English un-, from Proto-Germanic *un- (source also of Old Saxon, Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (source of Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), combining form of PIE root *ne- "not." Often euphemistic (such as untruth for "lie").
The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- (1) the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.
It also makes words from phrases (such as uncalled-for, c. 1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc., but the habit is not restricted to un-; such as put-up-able-with, 1812). As a prefix in telegramese to replace not and save the cost of a word, it is attested by 1936.
c. 1300, "conceal the personal identity of by changes of guise or usual appearance, with intent to deceive," from Old French desguiser "disguise, change one's appearance" (11c., Modern French déguiser), from des- "away, off" (see dis-) + guise "style, appearance," which is from Germanic (see guise).
From mid-14c. as "conceal or cover up the original character of by a counterfeit form or appearance." Originally primarily "to put out of one's usual manner" (of dress, etc.), "change one's appearance;" a sense preserved in phrase disguised with liquor (1560s) "being changed in behavior by intoxication."
It is most absurdly said, in popular language, of any man, that he is disguised in liquor; for, on the contrary, most men are disguised by sobriety. [Thomas De Quincey, "Confessions of an English Opium-Eater," 1856]
Related: Disguised; disguising.