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vigil (n.)[vigil 词源字典]: c. 1200, "eve of a religious festival" (an occasion for devotional watching or observance), from Anglo-French and Old French vigile "watch, guard; eve of a holy day" (12c.), from Latin vigilia "a watch, watchfulness," from vigil "watchful, awake, on the watch, alert," from PIE root *weg- (2) "be lively or active, be strong" (cognates: Old English wacan "to wake up, arise," wacian "to be awake;" Old High German wahta "watch, vigil;" see wake (v.)). Meaning "watch kept on a festival eve" in English is from late 14c.; general sense of "occasion of keeping awake for some purpose" is recorded from 1711.[vigil etymology, vigil origin, 英语词源]
vigilance (n.): 1560s, from Middle French vigilance (16c.), from Latin vigilantia "wakefulness, watchfulness, attention," from vigil "watchful, awake" (see vigil). Related: Vigilancy (1530s).
watch (n.): Old English wæcce "a watching, state of being or remaining awake, wakefulness;" also "act or practice of refraining from sleep for devotional or penitential purposes;" from wæccan (see watch (v.)). From c. 1200 as "one of the periods into which the night is divided," in reference to ancient times translating Latin vigilia, Greek phylake, Hebrew ashmoreth.
The Hebrews divided the night into three watches, the Greeks usually into four (sometimes five), the Romans (followed by the Jews in New Testament times) into four. [OED]

On þis niht beð fowuer niht wecches: Biforen euen þe bilimpeð to children; Mid-niht ðe bilimpeð to frumberdligges; hanecrau þe bilimpeð þowuene men; morgewile to alde men. [Trinity Homilies, c. 1200]
From mid-13c. as "a shift of guard duty; an assignment as municipal watchman;" late 13c. as "person or group obligated to patrol a town (especially at night) to keep order, etc." Also in Middle English, "the practice of remaining awake at night for purposes of debauchery and dissipation;" hence wacches of wodnesse "late-night revels and debauchery." The alliterative combination watch and ward preserves the old distinction of watch for night-time municipal patrols and ward for guarding by day; in combination, they meant "continuous vigilance."

Military sense of "military guard, sentinel" is from late 14c. General sense of "careful observation, watchfulness, vigilance" is from late 14c.; to keep watch is from late 14c. Meaning "period of time in which a division of a ship's crew remains on deck" is from 1580s. The meaning "small timepiece" is from 1580s, developing from that of "a clock to wake up sleepers" (mid-15c.).
watchful (adj.): c. 1500, waccheful, from watch (v.) + -ful. Related: Watchfulness.