They seem to me to be a bit of a combination of several, North-western European nations.
The Dialect and Accent seems to be mostly Irish
The clan structure seems to come from the old Scottish clan structure.
The Naval/Raiding culture stems from classic Scandinavian Vikings. (I don't know enough about the individual countries to know, but i'm sure there are big differences between the individual countries.)
The Religious aspects seem to be a combination of all the different Pagan religions of pre christianity europe but including a lot of Scandinavian Paganisms key terms, names, and phrases.