The geneological branches

In the southern Irish province of Munster, the point where mythology turns into history, can be said to start with a group of Q-Celtic speaking invaders who arrived in Ireland sometime between 325 B.C. and 50 B.C. [1], led by Mug Nuadhat. (O'Rahilly, p.42)

The descendants of Mug Nuadhat became known as the "Eoganacht", named after Mug's grandson Eogan.
Seven Eoganacht septs are claimed to descend from Eogan, branching from the genealogical tree 5 generations after him at the sons of Corc, roughly around 400 A.D.. (Byrne, p.178)

Each of those septs has spawned numerous modern day surnames:
* Eoganacht Chaisil - MacCarthy, O'Sullivan, plus later
            O'Dennehy, MacGillicudy, O'Callaghan, MacAuliffe
* Eoganacht Locha Lein - O'Moriarty
* Eoganacht Raithlind - O'Mahoney, O'Donoghue, plus later [2]
            O'Long, O'Neill, O'Duggan, O'Feehan,
            O'Leary, O'Donnell, Mongan, O'Connell, Lynch,
            O'Hea, O'Cohalane/O'Coughlan, O'Cannifree, O'Bogue, Cahalane, O'Cronin,
            O'Flahiffe, O'Flynn, Connelly, O'Callaghan
* Eoganacht Glendamnach - O'Keefe
* Eoganacht Aine - O'Kirby
* Eoganacht Arann (a.k.a. Ninussa) - extinct
* Eoganacht Ruis Argait - extinct
* (Eoganacht Airthir Chliach are added to some lists, perhaps erroneously - O'Dwyer, O'Quirke)

[The manuscript sources describing the early Eoganacht genealogical tree can be found here.]

These Eoganacht septs of Munster gradually seized power from the existing Erainn (a.k.a. Fir Bolg, a.k.a. Belgae) tribes who had previously invaded Ireland from Britain sometime around 500 B.C. [3].

While never being all-powerful, the various Eoganacht septs ruled Munster for many centuries until succumbing to the competing pressures of the Dal Cais (Brian Boru and the O'Briens), and the Cambro-Normans (the FitzGeralds, Earls of Kildare and Desmond) in the 11th and 12th centuries.

A Continental Origin?

A Continental origin would need to be pinpointed for the Eoganacht myths to hold up to historical examination. In his usual self-assured manner, Professor Thomas O'Rahilly speculates from whom, where and when the Goidels (i.e. Q-Celts) originated. Specifically, he pinpoints the Queryas region in France, which is directly adjacent to the Italian border, in the Alps.
The long passage will be quoted in full here, due to its importance (p. 207):
     "Several pieces of evidence, which we need not now discuss, unite in suggesting that the Goidels were connected with the south-east of Gaul, and it is there too, that we have found the Quariates, a tribe of Q-Celts, located. [Their name survives in the form of Queyras, the name of a place situated on the River Guil, a tributary of the Durance, in the department of Hautes-Alpes {near Briancon}. (p. 147)]
     We must suppose that, before sailing to Ireland, a body of Q-Celts first migrated from south-east Gaul to the western coast, just as the Helvetii and other tribes tried to do in 58 B.C. The most likely cause of such a wholesale migration would have been the pressure of neighboring enemies, whether these enemies were fellow Celts or Romans or Germans. If (which is not certain) the Continental Goidels were settled within the area which became the Roman province of Gallia Narbonensis, their migration to the western coast must have taken place not later than 120 B.C. In any event the Goidels must have left Gaul before 50 B.C., when the rest of the country was finally subjected to Roman rule."

Even if the Quariates are not the ancestors of the Irish Goidels, there are other possibilities in Europe. For instance, Professor Francis Byrne makes his own conjecture about where the Eoganacht may have originated:
     "The primeval tribal pattern seems to have been relatively undisturbed until the rise of the Eoganacht in the fifth century. Whether they were, as they claimed, a distinct racial group from the ubiquitous Erainn is uncertain: there are certain slight hints in the ogham inscriptions from the Waterford area that they and their vassals the Deisi may have been of relatively recent Gaulish origin." (p.72)
    "The name of the dynasty implies descent from a divine or human personage connected with the sacred yew tree, suggesting a parallel with the Gaulish 'yew people', the Eburones, whose 'leth-ri' Catuvolcus poisoned himself with yew after his defeat by Caesar." (p.181)
(The Eburones were a Belgae tribe who lived in present day Belgium, and were reported to be Germanic.)

The genetic evidence

Many people with Eoganacht surnames are part of the same Y-DNA cluster, called "South Irish R1b".
[More details about this genetic cluster can be found here.]

One interesting point to highlight is there is a genetic mis-match between the southern Goidels (the Eoganacht), and the northern Goidels (the Connachta, a.k.a. "Ui Neill"), even though their common mythology claim they both invaded Ireland at roughly the same time, and from roughly the same place. [4]

The genetic evidence so far has put much doubt into the theory of a widespread "Celtic" population movement from the Continent to Ireland.


* "Early Irish History and Mythology", Thomas F. O'Rahilly, 1946 - This is the seminal work on the subject, and while its portayal of distinct waves of Celtic invaders has been questioned, the book's detailed analysis of the period has not been surpassed.
* "Irish Kings and High-Kings", Francis J. Byrne, 1973, revised 2001 - Contains exquisite genealogical charts of the various Kingships of Ireland.
* "The Book of Munster", Rev. Eugene O'Keeffe translation, 1703 - I have not been able to determine if there are earlier or better translations, but this is the crucial manuscript for tracing the lineage of the Eoganacht. [LINK]
* "The Book of Irish Families Great & Small", Michael C. O'Laughlin, 1997 - Very useful for quickly finding the origin of a surname.
* "Ireland's History in Maps", Dennis Walsh - By far the best compilation of information about early Irish history on the web. [LINK]

[1] The Goidel's own origin tales as noted in the "Annals of the Four Masters", come close to matching the historical timeline:
* Tuathal Techtmar [LINK] (leader of the northern Goidels) is claimed to have become High King in 76 A.D.
* Mug Nuadhat (leader of the southern Goidels) is claimed to have invaded Munster in 123 A.D.
It was Tuathal's grandson, Conn "of the Hundred Battles", who supposedly killed Mug in the battle of Mag Lena.
However, the dates of the reigns of Tuathal and Mug, as well as the blurring of their identities with those of their grandsons Conn and Eogan, is a confusing area of study which still needs to be sorted out. (see O'Rahilly, p. 200)

[2] The Eoganacht Raithlind have so many offshoots because "The Book of Munster" includes excerpts from a 1320 poem commissioned by the O'Donoghue Mor, and is therefore more detailed. However, some of the surnames noted are also found in Erainn septs. In those cases, it's most likely the same surname had multiple origins, or else there are discrepancies in some of the ancient genealogies. (For instance, O'Cronin, O'Duggan, O'Flynn, O'Hea, O'Leary, and Lynch are also claimed as part of the Corcu Loigde sept.)

[3] O'Rahilly is able to pinpoint the arrival date of the Belgae based on Ptolomy's map of Ireland [LINK], which lists various tribes in Ireland that can clearly be tied to similar tribes in Britain:
    "In the account of Ireland preserved by Ptolemy, which we have dated ca. 325 B.C., the ascendancy of the Priteni has given way to that of the Erainn or Bolgi. It would thus appear that the overthrow of the Priteni by Bolgic invaders took place within the sixth-fourth centuries B.C." (p.84)

[4] It was only in later centuries, when the annalists were trying to validate the "Irishness" of the Goidels and create a common origin for most of the tribes of Ireland, that the Eoganacht and Connachta ancestry morphed into the one commonly known as the 'Milesian':
    "There can be no doubt that one of the chief motives of the Lebor Gabala was a desire to unify the country by obliterating the memory of the different ethnic origins of the people" (O'Rahilly, p.194)
The Milesian genealogies [LINK] traced the southern Goidel back to Eber, who with his brother Eremon of the northern Goidel, invaded Ireland approximately 1500 years B.C. (Eber and Eremon were the sons of "King Milesius" of Spain, who could trace his own origin back to Adam!)
A very thought-provoking analysis of the Milesian genealogies has been written by John McLaughlin [LINK], discussing the question of Spanish origin.

Originally posted: 2/22/06
Last revised: 5/20/08