Conlon—Conlan—Connellan
The Gaelic surname regularly anglicized as CONLON, is O'Connallain. It is a diminutive form of the ancient Celtic personal name, Conall. O'Connallain therefore means "the descendant of 'little Conall'."
The O'Connallains were an important family of County Roscommon. It is in this County and the adjacent Counties of Mayo and Sligo that today the greatest number of families of this name are to be found. Two modern place names, Bonnyconnellan, a seat of the ancient O'Connallain chieftains in the Barony of Gallen, County Mayo, and Cloonconnellan in the Barony of Kilmain commemorate the influence of the family in Connacht. However, the name is found nowadays all over Ireland. CONLON and CONLAN are the most common variant spellings in modern times. About ten per cent of the descendants of the O'Connallains spell the name "Connellan" and a number use the form "Conlin."
The family is noted in history for the number of ollavs and historians it produced. The Book of the Connellans, a medieval work in Gaelic, which treats of the genealogies of the Tirconnell families is a very valuable source of historical and genealogical lore.
It should be noted that the name Conlon was also mistakenly used in some public records to translate the Gaelic surname of another famous family, the O'Caoindealbhains, who were chiefs of Cineal Laoghaire in the district of Trim, County Meath. This name is more correctly anglicized as Quinlan or Quinlivan. They are descended from Laoghaire, the last pagan King of Ireland. They are however a completely distinct family from the Conlons of Roscommon and Connacht.
Among the famous O'Connallains of Irish history may be mentioned Thomas O'Connellan, bishop of Achonry from 1492–1508. Owen O'Connellan (1800–1869) was one of the most eminent Gaelic scholars of the nineteenth century. In more recent times Joseph Connellan, the noted Nationalist member of Parliament, was one of the pioneers of the Sinn Féin movement, of the Gaelic League and of the Gaelic Athletic Association in Ulster.