O'Gorman Derived from the Irish word for blue (gorm) Strongly based in Laois until the Norman invasion the clan moved to Clare and Monaghan and then eventually to Tipperary. Variations include Mac prefix as well as just Gorman which remains popular in Tipperary. |  |
O'Kelly From the original Ceallaigh which means bright-haired. The most famous of the Kelly/O Kelly clan was descended from Tadhg Mor O Ceallaigh who died in the Battle of Clontarf in 1014. |  |
O'Mahony A traditional Cork name, the OMahony clan retained power around Bandon until the 17th Century. The name deroves from the Irish word for bear, Mathghamhan |  |
O'Reagan The family name of Regan - of which OReagan is a variant - is derived from riodhgach which is the Irish for impulsive. The name is strong around Dublin/Meath, Limerick and Cork. In the Cork area the family was first strong in the Eastern part of the county around Fermoy (where a number of town names end directly regan)but later moved to West Cork. Variations of the name include Reagan and ORegan. |  |
O'Regan The family name of Regan - of which ORegan is a variant - is derived from riodhgach which is the Irish for impulsive. The name is strong around Dublin/Meath, Limerick and Cork. In the Cork area the family was first strong in the Eastern part of the county around Fermoy (where a number of town names end directly regan)but later moved to West Cork. Variations of the name include Reagan and ORegan. | |
O'Rourke Derived from the old Norse/Viking word for Hrothekr which means famous king which became adapted into Irish as Ruarc. The original Ruarc was a ninth century king and the family have a long association with Connaught...providing four Kings. |  |
O'Shea From the Irish word Seaghdha which means hawk-like. Holding power in Kerry during the Middle Ages, the name is still strongest in this area. A branch of the family migrated to Tipperrary and Kilkenny around the 14th century and the name is also common in those counties. |  |