unsecure (adj.)

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.

1530s, "without care or fear, dreading no evil" (a sense now archaic), from Latin securus, of persons, "free from care, quiet, easy," also in a bad sense, "careless, reckless;" of things, "tranquil; free from danger, safe," from *se cura, from se "free from" (see se-) + cura "care" (see cure (n.)).

In early use it often implied "over-confident, too sure." In English, in reference to places, "free from danger, unexposed," by c. 1600. The mechanical meaning "firmly fixed" (of material things) is by 1841, extended from the mental meaning "affording grounds for confidence" (1580s) hence "of such stability, strength, etc. to preclude risk." Of telephones or telephone lines, "not wiretapped," by 1961.

The earlier word, or form of the word, was Middle English siker, from Old English sicor, an earlier borrowing of the same Latin word, and sure (adj.) is a doublet, altered in its passage through Old French. Related: Securely.

1640s, "unsafe," also "not fully assured, not free from fear or doubt," from Medieval Latin insecurus, from in- "not" (see in- (1)) + Latin securus (see secure (adj.)). Psychological sense dates from 1935. (insecurity in the psychological sense dates from 1917.) Related: Insecurely.