O’Callaghan is an ancient Irish name and remains one of the most popular names in the country today. It is particularly prominent in counties Clare, Cork, Meath and Armagh.
There are a number of variations including Callahan, O’Callahan, Callaghan, Kelaghan, Keelaghan, Kealahan and several more.
The name derives from the name O’Ceallachain. Ceallach is an old Gaelic word that meant ‘contention’ or ‘strife’. However, the personal name Ceallach meant ‘bright headed’.
The ‘O’ prefix meant that the person was a ‘grandson of’ or ‘male descendent of’. So a person with the name O’Ceallachain was a descendent of Ceallach, who was a man of strife and contention.
This may well be true because the man in question was the king of Munster in the 10th century. King Ceallach a was also a chieftain of the Eoghanact. This was a consortium of the leading families of Munster. Ceallach is also said to have killed Cinneide, who was the father of future High King, Brian Boru.
The O’Ceallachains used to have territory in Co Cork at the Barony of Kinelea. They lost their power after the Anglo-Norman invasion and had to head north. They arrived at Mallow in the north of Co Cork and became a powerful family and were lords of the region.
They lost their territory in Mallow when Oliver Cromwell invaded Ireland. They moved along again, this time to Co Clare. In the 20th Century, some of the land that had been ruled by the O’Callaghans in this period was bought back by a descendent of the family, Donough O’Callaghan. The ancestral estate, which became known as Longueville House after the family that took it over, is now a luxury hotel back in the O’Callaghan’s hands.
A totally different clan formed in the north of the country. They lived in the counties Meath, Armagh, Louth and Monaghan.
Many O’Callaghans or Callaghans who emigrated to the United States dropped the g in the name to become ‘Callahan’ as they passed through Ellis Island in New York.
Over the centuries, thousands of O’Callaghans left Ireland and settled in Europe, America and Australia. There are still many people with the name in the UK, the US and Spain.