secure (adj.)

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.

c. 1600, "to make safe, guard from danger," from secure (adj.). Meaning "ensure, make certain, guarantee" is from 1650s; that of "seize and hold" (in reference to persons) is from 1640s; that of "make fast or firm" (of things) is from 1650s. The sense of "get possession of, make oneself master of" is from 1743. Related: Secured; securing.