This is a famous Irish surname. It is of dual origin. Firstly it may derive from the pre 10th century Gaelic surname O' Maolchaisil, which literally means 'The male descendant of the chief of Cashel' and hence a reference to the city and area known as Cashell in County Limerick. Secondly it can be from the Norman-English surname de Cashel, a major family of early settlers who from the 14th to the 17th century were prominent holders of great estates in County Louth. They were Catholic and pro-Irish and in consequence suffered serious losses during the Elizabethan period when all catholics were suspected of being the agent of foreign powers. The surname is recorded now in the 21st century usually as Cashell, sometimes as Cashill and Cassels, and even more rarely as Mulcastel and Mountcashel. Very few Gaelic surnames are locational, in fact only about a dozen out of some four thousand, so this is an unusual surname in several respects. Examples of recordings taken from surviving church registers include Daniell Cashell whose son Benjamin was christened at St Michan's church, Dublin, on September 11th 1643, and Bridget Cashill, who was christened at Kilmallock, County Limerick, on April 24th 1864.