Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
MERVYN
As described in historical dictionaries
Patronymica Britannica (1860)
MERVYN. Probably a baptismal name, as we find in Domesday Merefin, Merven, Mervinus, &c., as tenants prior to the making of that record. See Mirfin.