vigil (n.)

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- "to be strong, be lively." 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.