Vigilant

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late 15th century: from Latin vigilant- ‘keeping awake’, from the verb vigilare, from vigil (see vigil).

wiktionary

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From French vigilant or its source, Latin vigilans, present participle of vigilare(“stay awake”), from vigil(“awake”). Doublet of vigilante, from Spanish.

etymonline

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vigilant (adj.)

late 15c., from 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" (from PIE root *weg- "to be strong, be lively"). Related: Vigilantly.