1650s in figurative sense, from un- (1) "not" + past participle of ruffle (v.). Literal meaning, in reference to feathers, leaves, etc., is recorded from 1816.
Entries linking to unruffled
un- 1
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.
ruffle v.
early 14c., ruffelen, "to disturb the smoothness or order of," a word of obscure origin. Similar forms are found in Scandinavian (such as Old Norse hrufla "to scratch") and Low German (ruffelen "to wrinkle, curl;" Middle Low German ruffen "to fornicate"), but the exact relation and origin of them is uncertain. Also compare Middle English ruffelen "be at odds with, quarrel, dispute."
The meaning "disarrange" (hair or feathers) is recorded from late 15c.; the sense of "annoy, vex, distract" is from 1650s. Related: Ruffled; ruffling.