Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.
GILMOUR
As described in historical dictionaries
An Etymological Dictionary of Family and Christian Names (1857)
Gillemore, Gaelic, the henchman or follower of the chief, one who carried the chief's broadsword, from gille, a servant, and mor, large, great.
Patronymica Britannica (1860)
GILMOUR.
Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
Surname type: From name of parent
Origin: Celtic
Region of origin: British Isles
Country of origin: Ireland
Religion of origin: Christian
Language of origin: Gaelic