Recorded in a wide range of spellings including: Dallaghan, Dalligan, Dolligon, Dollihan, Dologon, Dullaghan and Dullighan, this is an Irish surname of antiquity. Originally from the pre 10th century Gaelic O'Dalachain meaning either the descendant of the son of the blind one, from the word "dall" or possibly from the word "dalach" meaning "assembly," which is also the base of the popular surname Daly. Irish surnames almost invariably originate from a nickname for the first nameholder and chief of the clan. Whilst a number relate to the deeds of famous warriors, the majority are more personal, and often seem to have a semi-religious or constitutional base, as with this one. It is said that before the Cromwellian period of the 17th century the clan were famed for their clerical prowess at a time when few could read or write. The epi-centre of the name was Clonmacnoise in County Offally on the banks of the Shannon River, but it seems that they were largely dispersed at that time of the "Plantations" in 1640 - 1660. What is certain is that for the past two hundred years the surname in its various forms has been centred on County Down, and it is from there that most recordings are to be found. The surname is also recorded in the the Famine Registers of 1846 - 1848, an example being James Dullion, who sailed from Newry for New York on the ship "Brothers" on April 23rd 1846. Earlier examples of the recordings from the church registers of Ulster include John Dollihan of Dromore on February 5th 1786, and Josias Dologon also of Dromore, on July 28th 1799.