O'reilly Family History
O'reilly Name Meaning
Irish: Anglicized form of Gaelic Ó Raghailligh ‘descendant of Raghailleach’, Old Irish Roghallach, a personal name of unexplained etymology. This is the name of a chieftain family in County Cavan, related to the O’Rourkes.
Source: Dictionary of American Family Names ©2013, Oxford University Press