MacCionnaith (P.137) under bright says the phrase bright starry night can be represented by oíche bhreacgheal [C M], fhionnagheal [M];

One is tempted to connect fhionnagheal with Fingal, in North County Dublin, but which is derived from fhine ghall, meaning "fair-haired foreigners."

But what is more interesting about the above is that fhionnagheal means "bright starry". geal is bright, so fionn must represent star or stars.

Our contention in Island of the Setting Sun is that certain mythical characters were in fact based on the constellation Orion, including Fionn Mac Cumhaill. In chapter 11, "Star Stories: Sky Myths of the Ancients", we report on page 237 that Fionn mac Cumhaill's name means "bright son of the hazel".

It could also mean "starry son of the hazel".