Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
GROUSE
As described in historical dictionaries
Patronymica Britannica (1860)
GROUSE. "Is certainly not from the bird, but from an old Germ, name Grauso, VI. cent., which Forstmaun refers to A-Sax. greosan, horrere." Ferguson.