Mcilroy — The Red-Haired Lad

McIlroy renders Mac Giolla Rua, joining giolla (‘lad’, ‘servant’) with rua (‘red-haired’). The chief family held Ballymackilroy in the parish of Aghalurcher, near Lough Erne in County Fermanagh. The same Irish original also produced McElroy, Gilroy and Kilroy — scribes heard one word and wrote down four.

One Gaelic name, four English spellings, and a family that never moved — the variation is the clerk's, not theirs.

Irish form: Mac Giolla Rua