Etymology: < Middle French, French alerte watchful, vigilant (16th cent.) < Middle French à l'herte , Middle French, French †à l'erte on the lookout, on the watch (1552; obsolete after 1676) < Italian all' erta on the watch, on the lookout (14th cent.; frequently in stare all' erta to stand on the watch), literally ‘at a high point’ < alla to the, at the + erta high point, promontory (often used as a lookout) (a1290), use as noun of feminine of erto raised, aloft (1282), use as adjective of past participle of ergere to raise up, to erect (13th cent. as †erçer ; < an unattested post-classical Latin variant *ergere (with elision of unstressed medial vowel) of classical Latin ērigere erect v.). Compare Spanish alerto , adjective (c1492), Portuguese alerta , adjective (16th cent.), both < Italian; also German alert (1631 as †allert ; earlier in non-naturalized form as all' erta (c1600 in sich all' erta halten to be vigilant); < Italian), Swedish alert (1635 as adverb (as †allairt ), 1672 as adjective, 1842 as noun; < French). With the semantic development, compare earlier alarm int., alarm n.The following two quots. show earlier occurrences, in an English context, of Spanish alerto , interjection (use as interjection of alerto , adjective) and Italian all' erta , interjection (use as interjection of all' erta , adverbial phrase):1590 R. Williams Briefe Disc. Warre 26 The Castilian drew his sword, crying Alerto to his Souldiers.1598 R. Barret Theorike & Pract. Mod. Warres Gloss. 249 Alerta, an Italian word, vsed vnto the souldiers, when there is any suspition of the enemy, and signifieth to be watchfull, carefull, and ready. With the use as noun, compare French alerte (end of the 17th cent. as interjection, used as a military warning cry, 1771 as noun), use as interjection and noun, respectively, of à l'erte (see above). Compare earlier alarm n.

Etymology: < alert adj. Compare French alerter (1836).