Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.
MCGREGOR
As described in historical dictionaries
An Etymological Dictionary of Family and Christian Names (1857)
The descendants of Gregor, who was the son of Alpin, King of Scotland. A family of great antiquity, and of distinguished ancestors. (See Gregor.)
Surname type: From name of parent
Origin: Celtic
Region of origin: British Isles
Country of origin: Scotland
Religion of origin: Christian
Language of origin: Gaelic