1590s, from un- (1) "not" + past participle of protect (v.).
Entries linking to unprotected
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.
protect v.
"cover or shield from danger, harm, damage, exposure, trespass, temptation, insult, etc.," early 15c., protecten, from Latin protectus, past participle of protegere "to protect, defend, cover over, cover in front" (source also of French protéger, Old French protecter, Spanish proteger). This is from pro "before" (from PIE root *per- (1) "forward," hence "in front of, before") + tegere "to cover" (from PIE root *(s)teg- "to cover").
Applied with a wide range, both literal and figurative. The sense in political economy, "guard or strengthen against foreign competition by means of tariffs, etc.," is by 1789. Related: Protected; protecting.