 In 1247 Maurice fitz Gerald , Justiciar of Ireland , invaded the territory of Maoilsheachlainn Ó Domhnaill , King of Tír Chonaill , defeating and killing this Irish king at the Battle of Ballyshannon . According to the Annals of Loch Cé , one of Maoilsheachlainn 's allies who died at Ballyshannon was a Mac Somhairle , a " Descendant of Somhairle " : 
