invigilator (n.)

"to watch diligently" (archaic), 1550s, from Latin invigilatus, past participle of invigilare "watch over, be watchful, be devoted," from in- "in" (from PIE root *en "in") + vigilare "to watch, keep awake, not sleep" (from PIE root *weg- "to be strong, be lively"). In late 19c. especially in reference to student exams. Related: Invigilated; invigilating.