Gaelic and Norse both use pap/pab sounding words for priests (as in Cairnpapple) also, the norse for an island was to put an -ay onto the end of the descriptive, as in Sanday in the Orkneys i.e. sandy island (easy! ...you now speak Viking).

There are enigmatic and fragmented literary sources for priestly communities on the northern islands ... some from Roman sources .... if I can remember right there is one record of the people being able to work at dawn and dusk but hiding underground at midday.. if you want I could find the exact quote.... and in one of the Icelandic sagas there is a tale of the first farm settlers finding evidence of previous settlement in the form of crucifix's, books and other religious paraphenalia that had been abandond...

....presumably the owners of these ended their days as slave labour at the dark end of a fjiord somewhere.

As you say, the Viking, always ones to turn a buck, were very active in the slave trade of their time.

FTC