grimumaþer (OSw) grímumaðr (ON) noun

Literally a masked man. In ON, one who beats and robs a householder at his home, and who could, as a result, himself be killed or outlawed. In OSw, one living in the forest where he robs someone, and who, if killed, was not compensated.

man in disguise ONorw FrL Mhb 62
robber in the forest OSw YVgL Drb Refs:

Schlyter s.v. grimumaþer