Family History and Genealogy Resources by Surname
McMahon Surname Origin
(origin Gaelic) The son of a bear; a hero.
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.
McMahon Surname Meaning and Family Facts
There is more to McMahon family history than the origin of your surname:
A McMahon Family History Thought:
'Those who forget their past are destined to repeat it.' --Robert A. Heinlein