Donnellan

Donnellan is an Irish surname and refers to the clan name Ó Domhnalláin.
At least two unrealated families of the name existed in Gaelic Ireland. One in south-east Ulster, another in south-east Connacht in the kingdom of Ui Maine.
The patron of the Donnellan's of Ui Maine is Saint Grellan. The family derive their name from Domnallan mac Maelbrigdi.