The surname Dempsey is generally accepted as being of Irish origins and therefore correctly O'Dempsey. There can be little doubt that most nameholders do derive originally from this source. However the name has also been long recorded in England, and there is a suggestion by eminent researchers that some of the English name holders may derive from some lost medieval village called 'Dempsey or Demsey', however this is not proven. The Irish clan, was once one of the most powerful in Ireland, possessing great estates in the area known as 'Clanmalier', now the modern counties of Leix and Offally. James 1st of England and V1 of Scotland granted Terence O'Dempsey the title of Viscount Clanmalier, for the support of the clan during the many rebellions of the 16th and 17th century. The name is an anglicised spelling of the Gaelic O'Diaomasach, which translates as 'The descendant of the proud one'. Curiously in 1170 the Chief of the Dempsey's opposed the landings of Strongbow, Earl of Pembroke, and, it is said, was the only Irish commander to be successful in such engagements. At sometime in the following centuries the clan became loyal to the English crown, a loyalty that ultimately lost them all their lands when they supported the catholic James 11 at the battle of the Boyne. Here he was defeated by William of Orange. Early recordings of the surname include Lewis O'Dempsey in 1652 in Ireland, and Thomas Dempsey, married at St Anne's church, Westminster, in 1692. The blazon the coat of arms is that of a red field, a lion rampant between two swords conjoined, hilts down. The first recorded spelling of the family name is shown to be that of Dermot O'Dempsey, which was dated 1193, founder of Monasterevan Abbey, during the reign of King Richard 1st of England, known as 'Lionheart', 1189 - 1199. 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.