1580s, "unpetitioned, not approached with a request," from un- (1) "not" + past participle of solicit (v.). Meaning "not asked for, unsought" is from 1680s.
Entries linking to unsolicited
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.
solicit v.
early 15c., soliciten, "to disturb, trouble, arouse, excite," from Old French soliciter, solliciter (14c.) and directly from Latin solicitare, sollicitare "to disturb, rouse, trouble, harass; stimulate, provoke," from sollicitus "agitated," from sollus "whole, entire" (from PIE root *sol- "whole, well-kept") + citus "aroused," past participle of ciere "shake, excite, set in motion" (from PIE root *keie- "to set in motion"). Related: Solicited; soliciting.
The meaning "to further (business affairs)" evolved mid-15c. from a French sense of "manage affairs." The meaning "entreat, petition" (someone, to do something) is attested from 1520s.
The sense in reference to women, "entice or lure to immorality," especially in reference to prostitutes seeking clients in public, is attested by 1710 but implied a century earlier (in solicitrix), perhaps with awareness of the business sense of the word, but it also had an earlier sense, in reference to men, of "to court or beg the favor of" (a woman) for immoral purposes, which is attested from 1590s.