In ancient Ireland the population was much smaller and the mass movement of people was uncommon. It was usual therefore to be known by only one name: Niall, Eoin, Art, etc. As long as there was no one else in the same area with the same name then there was no problem. The Gaelic Clan system was well established and gave individuals a common identity with the people of their tribe, and with the commonly shared area where they lived.
The single name system started breaking down in the 11th century when the population started growing and there was a need for further means of identification. With the increase in population the Clans eventually broke up into a number of distinct septs or groups. These groups were headed by an original member of the Clan and dominated a particular part of the countryside. It was not uncommon to find septs with the same name in entirely different parts of the country.
The vast majority of Gaelic Irish surnames were created during the 11th and 12th centuries. Surnames also provided permanent proof of verifiable blood ties. The names could also be used as a political asset as it demonstrated membership of a powerful kin-group.
The sept system became an integral part of Gaelic society and survived and was even expanded by the Norman invasion. It did not however survive the English invasion and colonization of the 17th century, when it became a disadvantage to have a Gaelic sounding name. With the transition to Anglo sounding names came misspellings and misinterpretations and resulted in the numerous variations found in Irish family names today.
Ireland was one of the first European countries in which a system of fixed hereditary surnames developed. The earliest names appear to be those incorporating ‘Ó’ or its earlier form ‘Ua’, meaning “Grandson”. The first recorded fixed surname is that of O’Clery (Ó Cleirigh), as noted in the Annals of Tighemeach Ua Cleirigh, Lord of Aidhne in Co. Galway in 916 A.D. It seems likely that this is the oldest surname recorded anywhere in Europe.
There are many different origins for Irish names today but the vast majority can be broken down into either of three categories: Gaelic Irish, Cambro-Norman, and Anglo-Irish. One important distinction between Irish and English surnames is it is extremely rare to find an Irish surname deriving from a locality while it is common in English surnames. It seems likely that the Gaels considered it much more important as to who you were related to then to where you came from.
It should also be noted that Scottish Gaels were actually descendants of Gaelic emigrants to Scotland. The word ‘Scotus’ is Latin for ‘Irishman’. Scottish settlers who moved to Ireland (especially Ulster) may already have been of Gaelic Irish descent.
Besides personal names, our Irish ancestors had even from pre-historic times, a complete system of fixed clan-names by which each family group could be identified. Below are a few examples.
Some words prefixed to the names of ancestors to form clan-names are as follows: Cineal -(Cinel, Cenel, angl. Kinel), kindred, race, as Cineal Eoghain, race of Eoghan. Clann – children, race, descendants as Clann Cholmain, race of Colman. Corca – race, progeny as Corca Dhuibhne, race of Duibhne. Dal – tribe, progeny as Dál gCais, race of Cass, whence “Dalcassian”. Muintear – family, people, as Muintear Mhaolmordha, family of Maoimordha. Siol, seed, progeny, as Siol Aodha Sláine, progeny of Aodha Sláine. Ua – grandsons, descendants, as Ua Néill, descendants of Niall.
Some word terminators used to form clan-names are as follows: -acht, as in Clanacht, race of Clann -na, as in Dealbhna, race of Dealbhaoth -ne, as in Conmhaicne, race of Comhac
Even today, the fact that all Gaelic names beginning with Ó or Mac (Mc), is undeniable proof of the significance of family and kin for the Irish people.