unlearned (adj.)

Old English leornian "to get knowledge, be cultivated; study, read, think about," from Proto-Germanic *lisnojanan (cognates: Old Frisian lernia, Middle Dutch leeren, Dutch leren, Old High German lernen, German lernen "to learn," Gothic lais "I know"), with a base sense of "to follow or find the track," from PIE root *lois- "furrow, track." It is related to German Gleis "track," and to Old English læst "sole of the foot" (see last (n.1)).

From c. 1200 as "to hear of, ascertain." Transitive use (He learned me (how) to read), now considered vulgar (except in reflexive expressions, I learn English), was acceptable from c. 1200 until early 19c. It is preserved in past-participle adjective learned "having knowledge gained by study." Old English also had læran "to teach" (see lere). Related: Learning.

"having knowledge gained by study," mid-14c., past-participle adjective from learn (v.) in its former transitive sense. Related: Learnedly; learnedness. "[L]earned expresses depth and fullness in the knowledge, while scholarly expresses accuracy" [Century Dictionary].

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.