In the Ulster Heritage DNA Project, we are starting to see several families with bona fide Norse, i.e. Viking, paternal ancestry. Two haplogroups that we see now are R1a and I1... both very Norse, usually from what is now Norway. The MacAvoy family from Antrim, surname in Irish (and Scots Gaelic) Mac 'a Buidhe, a shortened form of Mac Giolla Buidhe. Giolla = lad and in context, servant and Buidhe = Yellow (hair). You will find that a lot of the surnames from the southern Hebrides and Argyll come to us in these shortened forms. I am a Gaelic speaker, and one of the things you notice right off is, in northern Ulster and in Islay, Argyll, etc., there is a great tendencey to do this, to shorten words, not pronounce the endings.
It will drive a Gaelic student like myself to distraction, but gradually your ear gets used to it.
The Norse in Argyll, southern Hebrides, Donegal, Antrim, etc., to date seem to be mostly Norwegian in ancestry, judging from the DNA results. These families moved to the Irish sea area circa anno domini 850 to 1000. Were totally Gaelicised, i.e. became Gaelic speaking, Christian, adopted Gaelic folkways, within a couple of generations. (though this did not stop them from going 'a viking' during the heyday of the raids). A little know fact, many of the great Viking fleets were as much as 1/2 Gaelic in origin.
I'll post some more surnames of confirmed Gall Gael as I observe them. Gall Gael is just the old word for this group, and means 'stranger Gael.'