Family History and Genealogy Resources by Surname
McDonnough Surname Origin
(Origin Gaelic) The son of Donnach, the same as Duncan, safe, able to defend.
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.
McDonnough Surname Meaning and Family Facts
There is more to McDonnough family history than the origin of your surname:
A McDonnough Family History Thought:
'The only thing new in the world is the history you don't know.' --Harry S. Truman