Etymology Dictionary

ALERT,  on the watch.  (F.,—Ital.,—Lat.)   Alertness, Spectator, no. 566.   'The prince, finding his rutters [knights] alert, as the Italians say,' &c.; Sir Roger Williams, Act of the Low Countries, 1618, p. 87 (R.)—F. alerte, formerly allerte, and in Montaigne and Rabelais à l’erte, on the watch; originally a military term, borrowed from Italian in the 16th century (Brachet).—Ital. all’erta, on the watch; properly in the phrase stare all’erta, to be on one's guard.—Ital. alla (for a la), at the, on the; and erta, fem. of adj. erto, erect.—Lat. ad, prep. at; illam, fem. accus. of ille, he; and erectam, fem. accus. of erectus, erect.   See Erect.   ¶ The phrase 'on the alert' contains a reduplication; it means 'on-the-at-the-erect.'   Der. alert-ness.