I've just come back from my yearly jaunt to the emerald Isle, and met a very nice linguistics expert, whose hobby was ancient gaelic!! (whatever does it for you!!) And his twopenny worth is that the words are miss translated. The mysterious "Ballygran" is translated as - sort of "good home" -was the nearest he could explain, and the other reference to "In Kilkenny it is reported on marble stones there as black as ink" - is that it dates to the period where they were not allowed to practice their religion, and used to mark or lightly scribe the religious text on stone, so it could be "erased" when the need arose.