1560s, from French vigilance (16c.), from Latin vigilantia "wakefulness, watchfulness, attention," from vigil "watchful, awake" (from PIE root *weg- "to be strong, be lively"). Related: Vigilancy (1530s).
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.
"a vigil beside a dying person," 1865, from death + watch (n.) "a watching." The death-watch beetle (1660s) inhabits houses, makes a ticking noise like a pocket-watch, and was superstitiously supposed to portend death.
FEW ears have escaped the noise of the death-watch, that is, the little clicking sound heard often in many rooms, somewhat resembling that of a watch; and this is conceived to be of an evil omen or prediction of some person's death: wherein notwithstanding there is nothing of rational presage or just cause of terror unto melancholy and meticulous heads. For this noise is made by a little sheathwinged grey insect, found often in wainscot benches and wood-work in the summer. [Browne, "Vulgar Errors"]