Family History and Genealogy Resources by Surname
McWilliam Surname OriginThe son of William. See William
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.
McWilliam Surname Meaning and Family Facts
There is more to McWilliam family history than the origin of your surname:
A McWilliam Family History Thought:
'I don't have to look up my family tree, because I know that I'm the sap.' --Fred Allen