Recorded in at least the three spellings of Clandillon, Clendillon and Clondillon, this is an Irish surname. It is one which has defied the best efforts of researchers for the past century to come up with a wholly satisfactory expanation and etymology. The general opinion seems to be that it is a fused form of the surnames "Clan" and "Dillion", the first being a Scottish surname, and the latter both Scottish and Irish. However the very first known recording is believed to be in the year 1801, when one Mary Clondillion married at William Jones at St Michaels church, Limerick, on September 20th of that year. The famous Irish etymologist the late Edward MacLysaght, suggested that the name was "Wild Geese". That is to say a name which originally described Irish soldiers who served in the armies of (mainly) the king of France in the 18th century, and who later returned home. These people often adopted other surnames, perhaps to obscure their identity from the local officials. It has also been suggested that the name may have been locational from a now "lost" village, but if so no such name exists or existed. The nearest being Clondullan in County Cork. Given that most recordings of this name are to the north west, this is a possibility. Other early recordings include William Clendillon who married Rebecca Hynes also at Limerick, on November 15th 1814, and Robert Clandillion, the son of James Clandillon, who was christened at Banagher, County Offally, on November 11th 1865.