Curfew

A regulation requiring people to remain indoors between specified hours, or a time by which someone must return home.

From Old French 'covrefeu,' literally meaning 'cover fire' ('couvrir' = to cover + 'feu' = fire). In medieval times, this was the evening bell that signaled when people had to extinguish or cover their fires to prevent nighttime blazes that could destroy entire wooden towns. The bell became associated with the time everyone had to be inside and settled for the night. What started as a fire safety measure became a general evening restriction.