The late Irish Celt scholar (Thomas F. Ó Rahilly) states the following in his book Early Irish History and Mythology (1946, School of Celtic Studies; Dublin Institute for Advanced Studies): "(With) the Laginian (Celts) invasion of some 2,300 years ago...we get glimpses of a numerous invading band landing on the coast of Leinster, and of the death and destruction that followed in their wake. We see an Érnean king (Conaire) surprised and slain in his fortress, whether at Dinn Rig or at Tara, and we hear of another such king banished from his kingdom by the invaders." ---Thomas F. Ó Rahilly

The invading Laginian Celts (Laighin) defeated the Érainn (Fir Bolg or Belgae) Celts of Leinster with the latter unable to pay the high financial tribute demanded by the Laginian celtic chief leader. Thus the Érainn tribal groups (who lent their name to: Éire, Erin, Ireland and Hibernia) decided to leave their lands in Cos. Meath and Westmeath - crossing the Shannon River into southern Co. Roscommon and relocating within Connacht province (Galway, Mayo, Roscommon, Sligo, Clare) where other Érainn tribes welcomed them and gave them lands upon to live.

From these Érainn led by the sons of Úmor would come many famous surname septs that we know today. One of which is our own - Ó hAnnáin. But in that pre-christian era, there were no surnames as we know them - only tribal groups. Ireland would be first with the use of surnames but that would not come till the 10th and 11th centuries AD.

Ainninn, the surviving king and son of Úmor, led these tribesmen across the Shannon River westward out of Leinster and into Connacht province. This took place c.300 BC. It is from this migration that we find our pre-clan ancestors arriving in Connacht and Munster provinces. Ainninn whose name means "from the river/lake", is considered to be the source of our family sept name - Úa hAinninn - Ó hAnainn - Ó hAnain - Ó hAnnáin - which as we know later became anglicized as - Hannon or Hannan (with several variations).

In these pre-christian times, Co. Clare was considered a part of Connacht province along with Cos. Galway, Mayo, Leitrim, Roscommon and Sligo. Much later Co. Clare became part of Munster province, while Co. Galway at times fell under the control of the Érainn clans of Munster and/or the Laginian clans of Connacht. Such was the way things were when Ó hAnnáins (Hannon/Hannans) eventually found themselves aligned with ruling clans from both Connacht and Munster provinces that opposed each other.

Later, the Munster Ó hAnnáins were to be found amongst the Érainn Dalcassians - the Connacht Ó hAnnáins were to be found amongst the Laighin Ui Maine septs (tributes to the gaelic Ó Connors) where Galway/Roscommon and Mayo meet. Being a medium size sept (family), Ó hAnnáins took up residence in Roscommon, eastern Galway, southern Sligo and Mayo counties. Today these areas still have Ó hAnnáin - Hannon/Hannan populations.

As a sept/clan, perhaps the most notable Connacht "Hannon" was Maelisa Ó hAnáinn who served as Abbot of two monasteries in the towns of Athleague and Roscommon, Co. Roscommon. According to the Annals Of The Four Masters he passed away in the year 1266 AD.

The Annals written by four monks, also make mention of a Ó hAnain who was a "great priest" passing away earlier in 1235 AD (discovered by our own Elaine Hannon) and a Maelbrighde Úa hAinninn who was a "noble martyr and paragon of mildness and charity", passing away still earlier in 1133 AD (discovered by our own Pat Hannon). These three ancestors give us evidence that the Ó hAnnáins of Connacht once held the hereditary position of Airchinnech "Erenach" (ecclesiastical trustees & managers of church lands and properties) in Connacht.

This latter spelling of the sept name is particularly interesting to researchers, in that it shows the older spelling of the name (Úa hAinninn) that hints at how the Irish language was being spoken during the 1100s. By the early 1200s, we see when written the sept name has changed to Ó hAnnáin and Ó hAnain. Remember too that surnames were first used in Ireland and during this period of time were relatively new for all Irish septs/clans.

When the Griffiths Valuations of 1848-1864 took place, the results produced interesting rankings in Connacht province. Co Sligo overall ranked 2nd in number of Hannon/Hannans while Galway ranked 4th, Roscommon 5th, Mayo 7th, and Leitrim 15th. (Limerick in Munster ranked 1st overall in Hannon/Hannan population). This showed a continual shift in the Hannon/Hannan populations brought on by centuries of "transplantation".

[Note: The original gaelic spelling Ó hAnnáin was outlawed by the English Penal Laws (1691 - 1829), which in turn created the 'English' spellings of "Hannon" and "Hannan". Readers of this website should not be concerned by the use of two different English spellings. The correct Irish sept/clan name will always be -- Ó hAnnáin.]