Green’s Dictionary of Slang

(UK Und.) the dark.

c.1698		B.E. Dict. Canting Crew n.p.: Sneak c. goes upon the Sneak at Munns, c. he privately gets into Houses or Shops at Night, and Steals undiscover’d.
1718		C. Hitchin Regulator 20: The Munge, alias the Dark.
1725		New Canting Dict. [as cit. c.1698].
1768		(con. 1710–25) Tyburn Chronicle II in Groom (1999) xxix: The Munge The Dark.
2019		P. Baker Fabulosa 295/1: munge darkness.