1660s, "uncreated, without an origin," from un- (1) "not" + original (adj.). Meaning "derivative, second-hand" is recorded from 1774. Related: Unoriginality.
Entries linking to unoriginal
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.
original adj.
early 14c., "first in time, earliest," from Old French original "first" (13c.) and directly from Latin originalis, from originem (nominative origo) "beginning, source, birth," from oriri "to rise" (see origin). The first reference is to sin, synne original, "innate depravity of man's nature," supposed to be inherited from Adam in consequence of the Fall (the modern word order original sin is from 15c.). Also from late 14c., "pertaining to or characteristic of the first stage of anything. Meaning "produced directly by an author, artist, etc." is from 1630s; that of "fresh, novel, new, striking" is by 1782. Related: Originally.