This ancient Irish name is one of the Anglicized forms of the Gaelic "O Duibhuidhir", descendant of Duibhuidhir, a personal name composed of the elements "duibh", dark, black, with "odhar", sallow, tawny. The O' Dwyers were an important sept in County Tipperary; their lands were Kilnamanagh, the mountainous area lying between the town of Thurles and County Limerick. The O' Dwyers were always noted for their staunch resistance to English aggression, and many are recorded in this connection; Michael Dwyer (1771 - 1825) defied the English Government forces for five years, from 1798 to 1803, and was sentenced to transportation after his voluntary surrender. He eventually became a policeman in Australia. In America Joseph O' Dwyer (1841 - 1898) was noted as a pioneer physician, particularly in his contributions to the treatment of diphtheria, while William O' Dwyer, born in 1890, was an emigrant labourer from County Mayo who became Mayor of New York and a notable ambassador for the United States of America. The first recorded spelling of the family name is shown to be that of Denis Dwyre, witness, which was dated November 19th 1677, in "St. Peter and St. Kevin, Dublin", during the reign of King Charles 11, known as "The Merry Monarch", 1660 - 1685. 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.