night watchman

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A man who serves as a guard during the night.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun obsolete 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.
• noun A person who guards (usually at a building) at night.
• noun cricket The last batsman in a three or five day game to play on a particular day and thus carry over the batting to the following day.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a watchman who works during the night