This interesting name is a variant of "Devilly", itself the Anglicized form of the Gaelic "O'Duibhghiolla", composed of the elements "O", male descendant of, plus "dubh", black, and "giolla", lad. This is the name of two Co. Galway septs, the southern Ui Fiachrach and the Siol Anmchadha. Diffley and Deffely are both more usual in the adjoining county of Roscommon. Other variants of the name include Deely, Duffley, and Devally. A Margarett O'Deveny married John McKenley on November 26th 1657, at Derry Cathedral, Templemore, Londonderry, while James Deueny had a daughter, Ellin, christened here on July 16th 1659. At Derry Cathedral, Margarett, daughter of Donogh O'Deueny was christened on September 10th 1660. London church records show that Elizabeth, daughter of Robert and Anne Dufley was christened at St. Katherine by the tower, on December 15th 1746. John, son of John and Anne Diffley was baptised in the Rusbey District of Roscommon in Ireland on July 28th 1866. The first recorded spelling of the family name is shown to be that of Edmond O'Deveny, which was dated December 9th 1653, christening witness at Derry Cathedral Templemore, Londonderry, during the reign of Queen Mary, "Bloody Mary", 1553 - 1558. 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.