Mac Giolla Seanáin
Mac GIOLLA SEANÁIN, Mac GIOLLA SIONÁIN—IV—M'Gilsenane, M'Gylsinan, MacGillshenan, Gilshenan, Gilshenon, Gelshinan, Gilsenan, Gunshinan, Gilson, (Nugent, Leonard); 'son of Giolla Seanáin' (servant of St. Senan); a common surname in Meath, Cavan and Tyrone, but now often disguised under the anglicised forms of Nugent and Leonard, especially the former. Mag Uinnseanáin (which see) is a corruption. See also Mac Giolla tSeanáin which is a variant.
Alphabetical Index to Irish Surnames