night watchman

Short definition from Wiktionary

Noun

1. 1
   Prior to police forces, a person appointed by a town or city to walk the streets at night and guard the burghers from felons and robbers.
2. 2
   A person who guards (usually at a building) at night.
3. 3
   A lower order batter to play the last overs in low light to save better batters for the next day's play.
4. 4
   Alternative spelling of night watchman.