Green’s Dictionary of Slang

darkmans n.

[SE dark + -mans sfx]

1. [mid-16C–19C] (UK Und., also darkman, darkum) the night.

2. [early 19C] (UK Und.) a covered ‘dark’ lantern.

In compounds

darkmans budge (n.) [budge n.1 (1)]

[late 17C–early 19C] (UK Und.) a thief’s accomplice, who climbs into a house through a window and opens a door to admit the rest of the gang.