Clancy is an anglicization of the Olde Gaelic name Mac Fhlannchaidh, meaning "son of the red battle warrior" - a compound of the gaelic elements "mac" - a son, "flann" red or ruddy and "cath" - a battle. Some Clancys have resumed the Gaelic prefix "Mac" and become MacClancy. The main Clancy sept belonged to Co.Clare and parts of counties Limerick and Tipperary. The place name Cahermacclancy locates them in Co.Clare. A subsidiary sept belonged to Co.Leitrim. Many Clancys distinguished themselves abroad in Irigh Brigades. The first recorded spelling of the family name is shown to be that of MacFhlannchaidh. which was dated 1543, in Co.Clare. during the reign of King Henry V11, known as "Good King Hal", 1509 - 1547. 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.