McIlroy, McElroy, Gilroy, Mac Giolla Ruaidh A Gaelic surname meaning son of Giolla ruadh meaning ‘red (haired) youth’. A sept of Fermanagh whose chief resided at Ballymackilroy, in the parish of Aghalurchur near Lough Erne. Also a Scottish surname of similar derivation from the parish of Ballantrae in Ayrshire. It is also anglicised Gilroy which surname was principally found in Leitrim and Mayo in 1890 (estimated bearers 720). In 1890 McIlroy was principally found in Antrim, Down, Fermanagh and Derry, and the estimated number of bearers was 3,540 (all variants). In the United States Gilroy is the 8,390th most numerous surname with an estimated 2,750 bearers.
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