The Mac Carthys of Desmond are named from Carrthach (the son of Saerbhreathach), who is mentioned in the Irish annals as having fought the battle of Maelkenny, on the river Suir, in the year 1043; the O’Conors of Connaught from Conor or Concovar, who died in the year 971; the O’Molaghlins of Meath, the chiefs of the southern Hy-Niall race, from Maelseachlainn or Malachy II, monarch of Ireland, who died in the year 1022; the Magillapatricks or Fitzpatricks of Ossory from Gillapatrick, chief of Ossory, who was killed in the year 995, &c. &c.
From these and other evidences furnished by the Irish annals, it appears certain then that the most distinguished surnames in Ireland were taken from the names of progenitors who flourished in the tenth or beginning of the eleventh century. But there are instances to be met with of surnames which had been established in the tenth century having been changed to others which were called after progenitors who flourished at a later period, as O’Malroni of Moylurg, to Mac Dermot, and O’Laughlin, head of the northern Hy-Niall, to Mac Laughlin. There are also instances of minor branches of great families having changed the original prefix O to Mac and Mac O, or Mac I, when they had acquired new territories and become independent families, as O’Brien to Mac I-Brien, and Mac Brien in the instances of Mac I-Brien Arra, Mac Brien Coonagh, and Mac Brien Aharlagh, all off-shoots from the great family of Thomond; and O’Neill to Mac I-Neill Boy, in the instance of the branch of the great Tyrone family who settled in the fourteenth century eastward of the river Bann, in the counties of Down and Antrim.
This is all that we know of the origin of Irish surnames. Sir James Ware agrees with Keating and Gratianus Lucius that surnames became hereditary in Ireland in the tenth or beginning of the eleventh century; and adds, that they became hereditary in England and France about the same period.
Irish family names or surnames then are formed from the genitive case of names of ancestors who flourished in the tenth century, and at later periods, by prefixing O, or Mac, as O’Neill, Mac Carthy, &c. O literally signifies grandson, in which sense it is still spoken in the province of Ulster; and in a more enlarged sense any male descendant, like the Latin nepos: and Mac literally signifies son, and in a more extended sense any male descendant. The former word is translated nepos by all the writers of Irish history in the Latin language, from Adamnan to Dr O’Conor, and the latter, filius; from which it is clear that it is synonymous with the Welsh prefix Map (abbreviated to Ap), and with the Anglo-Norman Fitz, which Horne Tooke has proved to be a corruption of the Latin filius. Giraldus Cambrensis latinizes the name of the King of Leinster, Dermot Mac Murchadh, Dermitius Murchardides, from which it may be clearly perceived that he regarded the prefix Mac as equivalent to the Greek patronymic termination ides. The only difference therefore to be observed between O and Mac in surnames is, that the family who took the prefix of Mac called themselves after their father, and those who took the prefix O formed their surname from the name of their grandfather. Ni, meaning daughter, was always prefixed to names of women, as O and Mac meant male descendants; but this usage is now obsolete.
It is not perhaps an unlikely conjecture that at the period when surnames were first ordered to be made hereditary, some families went back several generations to select an illustrious ancestor on whom to build themselves a name. A most extraordinary instance of this mode of forming names occurred in our own time in Connaught, where John Mageoghegan, Esq. of Bunowen Castle, in the west of the county of Galway, applied to his Majesty King George IV. for licence to reject the name which his ancestors had borne for eight hundred years from their ancestor Eochagan, chief of Kinel Fiacha, in the now county of Westmeath, in the tenth century, and to take a new name from his more ancient and more illustrious ancestor Niall of the Nine Hostages, monarch of Ireland in the fourth century. His majesty granted this licence, and the son of John Mageoghegan now called John Augustus O’Neill, that is, John Augustus, DESCENDANT of Niall of the Nine Hostages. The other branches of the family of Mageoghegan, however, still retain the surname which was established in the reign of Brian Boru as the distinguishing appellative of the race of Fiacha, the son of Niall of the Nine Hostages, and the ancestor from whom the Mageoghegans had taken their tribe name.
From the similarity and almost complete identity of the meanings affixed to the words O and Mac in surnames, it might be expected that they should be popularly considered as conferring each the same respectability on the bearer; yet this is far from being the case, for it is popularly believed in every part of Ireland that the prefix O was a kind of title among the Irish, while Mac is a mark of no distinction whatever, and that any common Irishman may bear the prefix Mac, while he must have some claims to gentility of birth before he can presume to prefix O to his name. This is universally the feeling in the province of Connaught, where the gentry of Milesian descent are called O’Conor, O’Flahertie, O’Malley, &c.; and the peasantry, their collateral relatives, Connor, Flaherty, Malley. All this, however, is a popular error, for the prefix O is in no wise whatever more respectable than Mac, nor is either the one or the other an index to any respectability whatever, inasmuch as every single family of Firbolgic, Milesian, or Danish origin in Ireland, is entitled to bear either O or Mac as the first part of their surname. It is popularly known that O’Neill was King of Ulster, and O’Conor King of Connaught, and hence it is assumed that the prefix O is a title of great distinction; but it is never taken into consideration that O’Hallion was the name of the Irish Geocach or beggar who murdered O’Mulloy of Feara-Keall in the year 1110, or that Mac Carthy was King of Desmond or Mac Murrough was King of Leinster! It is therefore a positive fact that the prefixes O and Mac are of equal import, both meaning male descendant, and that neither is an indication of any respectability whatever, except where the pedigree is proved and the history of the family known. To illustrate this by an example: The O prefixed to my own name is an index of my descent from Donovan, the son of Cathal, Chief of the Hy-Figeinte, who was killed by Brian Boru in the year 977; but the Mac prefixed in the surname Mac Carthy is an indication of higher descent, namely, from Carrthach, the great-grandson of Callaghan Cashel, King of Munster, whose descendants held the highest rank in Desmond till the civil wars of 1641.
It would be now difficult to show how this popular error originated, as the meanings of the two prefixes O and Mac are so nearly alike. It may, however, have originated in a custom which prevailed among the ancient Irish, namely, that, for some reason which we cannot now discover, the O was never prefixed in any surname derived from art, trade, or science, O’Gowan only excepted, the prefix Mac having been always used in such instances, for we never meet O’Saoir, O’Baird; and surnames thus formed, of course never ranked as high among the Irish as those which were formed from the names of chieftains.
It may be here also remarked, that the O was never prefixed to names beginning with the word Giolla. I see no reason for this either, but I am positive that it is a fact, for throughout the Annals of the Four Masters only one O’Giolla, namely, O’Giolla Phadruig, occurs, and that only in one instance, and I have no doubt that this is a mere error of transcription.
Another strange error prevails in the north of Ireland respecting O and Mac, viz. that every name in the north of Ireland of which Mac forms the first part, is of Scotch origin, while those to which the O is prefixed is of Irish origin; for example, that O’Neill and O’Kane are of Irish origin, but Mac Loughlin and Mac Closkey of Scotch origin. But it happens in these instances that Mac Loughlin is the senior branch of the family of O’Neill, and Mac Closkey a most distinguished offshoot from that of O’Kane. This error had its origin in the fact that the Scotch families very rarely prefixed the O (there being only three instances of their having used it at all on record), while the Irish used O tenfold more than the Mac. This appears from an index to the genealogical books of Lecan, and of Duald Mac Firbis, in the MS. library of the Royal Irish Academy, in which mention is made of only three Scotch surnames beginning with O, while there are upwards of two thousand distinct Irish surnames beginning with O, and only two hundred beginning with Mac.
Another strange error is popular among the Irish, and those not of the lowest class, namely, that only five Irish families are entitled to have the O prefixed; but what names these five are is by no means agreed upon, some asserting that they are O’Neill, O’Donnell, O’Conor, O’Brien, and O’Flaherty; others that they are O’Neill, O’Donnell, O’Kane, O’Dowd, and O’Kelly; a third party insisting that they are O’Brien, O’Sullivan, O’Connell, O’Mahony, and O’Driscoll; while others make up the list in quite a different manner from all these, and this according to the part of Ireland in which they are located; and each party is positive that no family but the five of their own list has any title to the O. None of them would acknowledge that even the O’Melaghlins, the heads of the southern Hy Niall race, have any claims to this prefix, nor other very distinguished families, who invariably bore it down to a comparatively late period. On the other hand, it is universally admitted that any Irish family from Mac Carthy and Mac Murrough, down to Mac Gucken and Mac Phaudeen, has full title to the prefix Mac; and for no other reason than because it is believed to have been a mark of no distinction whatever among the ancient Irish. This error originated in the fact that five families of Irish blood were excepted by the English laws from being held as mere Irishmen. But of this hereafter.