late 14c., from un- (1) "not" + past participle of polish (v.). In reference to style, language, etc., attested from late 15c. Less common impolished is attested from 1580s.
Entries linking to unpolished
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.
polish v.
early 14c., polishen "make smooth or glossy" by friction or coating (of the surface of wood, stone, metal, etc.), from Old French poliss-, present participle stem of polir (12c.) "to polish, decorate, see to one's appearance," from Latin polire "to polish, make smooth; decorate, embellish;" figuratively "refine, improve," said by Watkins to be from PIE root *pel- (5) "to thrust, strike, drive," via the notion of fulling cloth, but there are other guesses.
The figurative sense of "free from coarseness, to refine" in English is recorded from mid-14c. Compare polite. Related: Polished; polishing. To polish off "finish" is by 1829 in pugilism slang, probably from the application of a coat of polish as the final step in a piece of work.