The book Arran; - Cook Clan

EARLY ARRAN ii
Finally the pressure of the Dalriadic Scots on the west,
expanding eastwards as they had expanded north, combined
with cruel blows on the divided Pictish kingdom by a new
overseas enemy on the eastern flank, ended in the conquest
of Pictland by the Dalriadic Kenneth MacAlpin in 843-4 a.d.
and the appearance of a united kingdom of Picts and Scots,
which was to take the name of Alba, and out of which was
to unfold the historic kingdom of Scotland.
IV
This new enemy, which had struck the Picts at a most
unfavourable moment, was a northern people, the Danes,
who, for some time, had been making buccaneering visits
round the coast and had even found their way up the Irish
Sea, with disastrous results to the richer monasteries of the
Celtic Church on the islands. In the western isles of Scotland,
however, it is mainly their neighbours of Norway, akin in
race and speech, who play the same part. Later a distinction
appears between Finn-gall, ' white-strangers,' or Norse, and
Dubh-gall or ' black-strangers,' the Danes ; on what grounds
of difference we do not know. But so far as western Scotland
is concerned it is really the Norse who matter, and finally
it is so even in Ireland. They were the readier to pass from
plunder to settlement ; even the western isles had attractions
for them, when compared with their own bleaker homes in
the north. At first, too, the roving bands may have been
they were not invincible, and both
ready to come to terms ;
in Ireland and England suffered many rebuffs ; we are told
that Kenneth MacAlpin had Norse aid in his campaigns upon
Pictland, and the name of Gofraith MacFergus as a king in
the isles about 852 even indicates a mixing of the peoples,
for the name is part Norse and part Gaelic. Out of such
mixing came the western folk of the coast who were known
as Gall-Gael.