In the Kingdom of the Hebrides they were known as Clann-Somhaire taking the name under ancient Brehon Law from their common great-grandfather.
He had no permanent connection to the O'Neill Dynasty, but was in fact closely related to the McMahon clans and the O'Reillys.
In 1898, Angus and Archibald MacDonald in their psuedo-history Clan Donald made an attempt to document the genealogy of the McDonnell of Cnoc na Cloiche.
Nor did the authors realize that McDonnell chieftains were selected under Brehon Law of tanistry, not English primogeniture.
The McDonnells had a long history with Ireland, which many now believe dates back to the ninth century Vikings.
Donnell, from whom the family takes its name, was slain in Ireland in 1246 while assisting O'Donnell king of Tir-Connail in battle against the English.