Recorded in various forms this interesting and rare surname is of Irish Gaelic origins. It is derived from the ancient pre 10th century O'Ciarain or O'Ceirin, composed of the prefix "O", meaning male descendant of, and a personal name derived from the word "ciar", meaning black or dark brown, and a reference to hair or skin colour. The sept were originally in possession of the greater part of the present barony of Costello in County Mayo, but during the medieval period their importance diminished. An inquisition in 1609 describes them as erenaghs, or hereditary holders of church property at Killaghtee in the diocese of Raphoe, in County Sligo. Today Kieran and O'Kieran are found mainly in County Mayo, where the name is also recorded as Kearns, O'Kerin, Kerrane, Kerin, Kerrin, Kirren, Kirrens, Kirrane, and Kearon. Thomas, son of Edward and Hannah Kerrans was christened on December 20th 1734, in Dublin, and Thomas Kerans married Charity Hard on May 21st 1805, in London. The Coat of Arms most associated with the family depicts a silver chevron with three red leopards' faces on a green shield, and the Motto is "Fidens et Constans", translating as "Courageous and Faithful". The first recorded spelling of the family name is shown to be that of Dorby Keran, which was dated April 6th 1654, marriage to Isma Beshell, at St. Michen, Dublin, Ireland, during the reign of Oliver Cromwell, known as "The Great Protector", 1649 - 1658. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.