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c.1600, from French précaution (16c.) and directly from Late Latin praecautionem (nominative praecautio) "a safeguarding," from past participle stem of Latin praecavere "to guard against beforehand," from prae "before" (see pre-) + cavere "to be one's own guard" (see caution (n.)). The verb meaning "to warn (someone) in advance" is from c.1700.