Family History and Genealogy Resources by Surname
McIlroy Surname Origin
(Origin Gaelic) From Mac, gille, and ruadh, red-haired;--the son of the red-haired young man.
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.
McIlroy Surname Meaning and Family Facts
There is more to McIlroy family history than the origin of your surname:
A McIlroy Family History Thought:
'If man cares not for his roots, then how can he care for his branches?' --Doyle M Davis