The bell rung in the reigns of William I. and II. at sunset, to give notice to their subjects that they were to put out their fires and candles (French, couvre feu, cover-fire). The Klokans in Abo, even to the present day, traverse the towns crying the “go-to-bed time.” Those abroad are told to “make haste home,” and those at home to “put out their fires.” Abolished, as a police regulation, by Henry I.
“The curfew tolls the knell of parting day.”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894