Family History and Genealogy Resources by Surname
O'Mahony Surname Origin
The descendant of Mahon, which signifies a bear.
Source: An Etymological Dictionary of Family and Christian Names With an Essay on their Derivation and Import; Arthur, William, M.A.; New York, NY: Sheldon, Blake, Bleeker & CO., 1857.
O'Mahony Surname Meaning and Family Facts
There is more to O'Mahony family history than the origin of your surname:
A O'Mahony Family History Thought:
'The past isn't dead. It isn't even past.' --William Faulkner