|Author||Rev Patrick Woulfe|
|Source||Irish Names and Surnames|
Ó MANACHÁIN, Ó MACHÁIN—I—O Managhane, O Manahan, O Monaghan, Monaghan, Monahan, Manahan, etc., Monk, Monks; 'descendant of Manachán' (diminutive of manach, a monk); the name of a Connacht family who derive their descent from Manachán, a famous warrior mentioned by the Four Masters at the year 866, and were chiefs of Ui Briuin na Sionna, in the barony of Ballintober, Co. Roscommon, until the year 1249, when they were ousted by the O Beirnes. The name at the end of the 16th century was very scattered. It is sometimes pronounced Ó Mionacháin and Ó Muineacháin, which see.
Alphabetical Index to Irish Surnames