As described in historical dictionaries

Patronymica Britannica (1860)

PHIN. A Gaelic personal name. Mac Phinn, or Mac Finn, is still found in the Highlands.

Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.


BritishSurnames.uk is a Good Stuff website.