Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
GREG
As described in historical dictionaries
Patronymica Britannica (1860)
GREG. See Gregory. Gregg of Norclifte Hall, co. Chester, claims from the clan iMacgregor of Scotland. Kings James VI. (I) and Charles I. issued edicts against the clan Gregor, denouncing the whole clan, and forbade the use of the name; in consequence of which mau}' of the race became Campbells, Gregorys, Greigs, and Gregs. B.L.G.