It's a case by case basis, just as with everywhere else, including the places called nordic today
"The blond Nordic element to-day predominates in Ireland as much as in England. It is derived, to some extent, from the early invaders of Celtic speech, but the Goidelic element has been in Ireland, as in England and Scotland, very largely absorbed by the Iberian substratum of the population, and is found to-day rather in the form of Nordic characters in brunets, than as the pure blond individuals who represent later and purer Nordic strains. The combination of black Iberian hair with blue or gray Nordic eyes is frequently found in Ireland and also in Spain, and in both these countries is greatly admired for its beauty.
The tall, blond Irishmen are to-day chiefly Danish with the addition of English, Norman, and Scotch elements, which have poured into the lesser island for a thousand years, and have imposed the English speech upon it. The more primitive and ancient elements in Ireland have always showed great ability to absorb newcomers, and during the Middle Ages it was notorious that the Norman and English colonists quickly sank to the cultural level of the natives. Indications of Paleolithic man appear in Ireland frequently as unit characters, as well as individuals. Being, like Brittany, situated on the extreme western outposts of Eurasia, it has more than its share of generalized and low types surviving in the living populations, and these types, the Firbolgs, have imparted a distinct and very undesirable aspect to a large portion of the inhabitants of the west and south, and have greatly lowered the intellectual status of the population as a whole.'