Recorded in many spelling forms including MacIllroy, MacElroy, McIlroy, McElroy, McGilroy, McAlroy and others, this is both a Scottish and Irish surname. It is an anglicized spelling form of the Gaelic "Mac Giolla Ruaidh", composed of the elements "Mac", meaning son of, "giolla", the youth, and "ruaidh", red haired; hence, "The son of the red haired youth". The sept originated in County Fermanagh, Ireland, where the placename Ballymackilroy is found: Their territory was on the east side of Lough Erne. There is another Ballymackilroy in County Tyrone and a further Ballymacilroy in County Antrim. Traditionally, Irish family names are taken from the heads of tribes, revered elders, or from some illustrious warrior, presumably the first of this clan had very prominent appearance, in addition to his youthfulness. The clan were of some status in Gaelic Ireland, particularly in the 15th Century, as their frequent mention in the Annals of the Four Masters and Loch Ce testifies. Rev. John McElroy, S.J. (1782 - 1877), was a native of County Fermanagh, where he was educated at a hedge school and was associated with the United Irishmen in 1798. He was famous in America as a missionary priest and church builder. Mary McElree was recorded in Maghera, County Derry, on June 5th 1845, and James McElrea at Cappagh by Omagh, County Tyrone on April 3rd 1855. On March 13th 1846, Mrs. Ellen McElroy, along with her children, John (19 yrs.), William (15 yrs.), Sally (14 yrs.), and Charles (12 yrs.), famine emigrants, departed from Liverpool aboard the "Ohio", bound for New York. The first recorded spelling of the family name is shown to be that of Michael M'Gilrey, which was dated 1376, in the "Ancient Charters of the Earldom of Morton", during the reign of King Robert 11 of Scotland, 1371 - 1390. Throughout the centuries surnames in every country have continued to "develop", often leading to astonishing variants of the original spelling.