This is an anglicized form of the Irish Gaelic surname O'Cathalain. Recorded in manyspellings including the popular Callan, Cahillane, and Cahalane, and the rarer Cahalune and Cahalin, the surname almost everywhere seems to have lost the Gaelic prefix of "O". This formerly indicated a "male descendant of", plus in this case the personal name Cathalain - meaning "the little brave warrior", a nickname of the first chieftain of the clan, probably around the 10th century a.d.. The personal name is a compound of the elements "cath", meaning a warrior, with "cal", meaning brave and the diminutive suffix "ain". There were originally three distinct septs of this clan in Ireland. The most important, in the 13th century, belonged to the ancient territory of Oriel which comprised the modern counties of Armagh, Monaghan and parts of South Down, Louth and Fermanagh. Here today the spelling as Callan is most popular. County Limerick was the orginal homeland of the Munster sept, and here the usual spelling was Culhane, with Cahillane and Cahalane in Cork and Kerry. The third sept was located in Co. Roscommon. Examples of the surname recordings include Catherine Cahillane, who married Jeremiah Callaghan at Killarney church on February 5th 1795, John Cahalan, a witness at Athenry, Galway, on March 28th 1864, and Patrich Cahalin, christened at Leitrim, County Leitrim, on May 21st 1866. The first recorded spelling of the family name is shown to be that of Cathalan, King of Farney. which was dated 1028, in Salin. during the reign of High Kings of Ireland "with opposition", 1022 - 1166. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.