December 8 is the commemoration of a Saint Fionan. He is remembered in the Martyrology of Donegal as:
8. F. SEXTO IDUS DECEMBRIS. 8.
FIONAN CUAE. He may be Fionan, of Druim-habhradh, son of Garbhan, who is of the race of Aenghus, son of Nadfraech, king of Munster.
and in the Martyrology of Gorman as:
Finan of Caue, a dear man.
There are a number of saints who bear this name in the Irish calendars and I hope that with a bit more research it may be possible to find out something more about this particular one.