Irish Surnames

Tracing the family tree has a long history in Ireland where in Celtic times, each family employed its own seannachie or genealogist, to record the lines of descent.

Ireland was one of the first countries to evolve a system of hereditary surnames. They came into general use in the eleventh century, although, a few were formed before the year 1000. The traditional belief that the system was introduced deliberately be the High King Brian Boru is without foundation; it developed spontaneously in Ireland, as elsewhere, as the population increased and the former practice, first of single names and then of transitory patronymics or nicknames proved insufficient.

At first the surname was formed by prefixing Mac to the father's Christian name or O to that of a grandfather or earlier ancestor, Fitz was from the French fils meaning son. A girl added Ni before her father's name, while her mother prefixed Ban.

After a time other types of surnames were adopted, still with the prefix Mac and sometimes O: for example those which introduced the words 'giolla' and 'maol' both usually meaning follower or servant, often in the sense of a devotee of some saint.....Mac Giolla Mhártain (modern Gilmartin or Martin) or Ó Maoilbhreanainn (modern Mulrennan) from St. Martin and St. Brendan. Names beginning with 'Gil' or 'Kil' are anglicized forms of 'Mac Giolla' and usually are translated as 'Son of the devotee of'. When 'Mac Giolla' is followed by an epithet, 'giolla' may be translated as lad or fellow: for example the name Mac Giolla Riabhaigh (the modern Mac/Mc Areavy) means the son of a gray or brindled lad or fellow.

The numerous of the later names were those formed from the occupation of the father, an example Mac an Bháird, son of the bard (modern MacWard and Ward) or Ó hÍceadga--icidhe, doctor or healer--(modern Hickey).

Less often, the Mac or O were prefixed to some word denoting character or peculiarity of the father or grandfather, Mac Dubhghaill, black stranger (modern Mac Dowell). From this it was a short step to the incorporation of nicknames in permanent surnames, for instance Mac an Mhadaidh--mada, dog (now MacAvaddy and the related name Ó Madáin, Madden).

This practice eventually led in some cases to the loss of the surname proper and the substitution of the nickname or characteristic for it. Because of this Irish surnames arose without the distinctive Mac or O; thus bán (white) became Bane, ruadh (red) Roe, láidir (strong) Lawder, and so on.

A note about Mac vs. Mc. The Gaels of Scotland are the descendants of the Gaelic settlers from Ireland. It seems not to be generally know that Scotland got its name from them, the word Scotus being Latin for Irishman. There seems to be a fallacy that Mc is Irish and Mac is Scottish. The practice of differentiating between Mac and Mc (and the now almost obsolete M') is fortunately dying out. There is no difference: Mc is simply an abbreviation of Mac.

For convenience, many people use the words sept and clan interchangeably, although strictly speaking it was the sept, rather than the clan, that was the dynastic system in Ireland. The sept comprised a group whose immediate ancestors had a common name, lived in the same locality, and who shared a common chieftain.

The above information was gathered from several sources including:

The Surnames of Ireland by Edward MacLysaght.

A Little Book of Irish Family Names by Ida Grehan.

The Dictionary of Irish Family Names by Ida Grehan.

Book of Irish Names: First, Family & Place Names by Ronan Coghlan, Ida Grehan & P.W. Joyce.

The Great Families of Ireland by The Irish Genealogical Foundation.

You may visit my research on the history of the surnames O'Downey and O'Reilly by clicking here to obtain information about those Irish surnames.
There is also another permanent page within my website regarding the surname O'Fallon.
You many visit that page by clicking here.