This name, with variant spellings Kelliher and Kelleher, is an Anglicized form of the Old Gaelic O'Ceileachair. The Gaelic prefix "O" indicates "male descendant of", plus the personal byname Ceileachair meaning "companionable" or "uxorious". The O'Ceileachair clan were of the population group, Dal gCais, otherwise called the Dalcassians, and they belonged to the ancient territory of Tuathmhumhan comprising most of the modern County Clare with adjacent parts of Counties Limerick and Tipperary. The family claim descent from one, Ceileachar, nephew of Brian Boru, High King of Ireland, 1002 - 1014. Maolmuire Mac (son of) Ceileachair compiler of the ancient "Book of the Dun Cow" belonged to the pre surname period. In the 14th Century the clan left their original habitat and settled in Counties Cork and Kerry where the name is most numerous today. On February 18th 1798, Cornelius Kelleher, an infant, was christened in Killarney, County Kerry, and on July 21st 1844, Mary Kalaher and Henry Akerman were married in St. James, Paddington, London. The first recorded spelling of the family name is shown to be that of William Killeher, (christening), which was dated July 31st 1757, Macroom, County Cork, during the reign of King George 11 of England, "The Last Warrior King", 1727 - 1760. 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.