vigilant (adj.)youdaoicibaDictYouDict[vigilant 词源字典]
late 15c., from Middle French vigilant or directly from Latin vigilantem (nominative vigilans) "watchful, anxious, careful," present participle of vigilare "to watch, keep awake, not to sleep, be watchful," from vigil "watchful, awake" (see vigil). Related: Vigilantly.[vigilant etymology, vigilant origin, 英语词源]