Ó Donnghalaigh
Ó DONNGHALAIGH—I—O Donnowly, O'Donnelly, Donnelly, &c.; 'descendant of Donnghalach' (derivative of Donnghal); the name (1) of a Tipperary family who were anciently chiefs of Muscraighe-Thire, now the barony of Lower Ormond, but disappeared from history towards the end of the 11th century; and (2) of a Galway family, a branch of the Siol Anmchadha, who were numerous in that county at the beginning of the 17th century. This surname is also written Ó Dúnghalaigh. Its anglicised forms cannot now be distinguished from those of Ó Donnghaile, which see.
Alphabetical Index to Irish Surnames