Where the Gleeson surname comes from, how the Gleesons of Ormond fit into Brian Boru’s world, and which DNA test settles the Dál gCais question.

The Gleesons (Ó Glasáin, later Ó Gliasáin) take their name from Glasán, a diminutive of glas, meaning grey or green. Their homeland was Lower Ormond and the old country of Arra in north Tipperary, close to Nenagh and the eastern shore of Lough Derg. Gleeson is still one of the most common names in Tipperary, and the surname is spread right across Munster.

Gleeson at a glance

  • Irish form: Ó Glasáin, later Ó Gliasáin
  • Meaning: descendant of Glasán, from glas, “grey” or “green”
  • Homeland: Lower Ormond and Arra, around Nenagh, County Tipperary
  • Kindred: the Aradh, whose country later passed to the O’Briens of Arra
  • Found today: mainly Tipperary, Limerick, Clare and Cork
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Origin of the name

Patrick Woulfe gives the original form as Ó Glasáin, “descendant of Glasán”, and calls it a common surname across the south of Ireland, especially in Cork, Limerick, Tipperary and Kilkenny. Edward MacLysaght adds the detail that matters for Brian Boru researchers. The main Gleeson sept lived in Lower Ormond, and the family belonged to the Aradh, the people whose territory later became Mac Uí Bhriain Aradh’s country. That was the lordship of the O’Briens of Arra, a branch of Brian Boru’s own descendants.

So the Gleesons lived for centuries under O’Brien lords, but the old pedigrees don’t make them Dalcassian by blood. That is where DNA has changed the picture.

The Gleesons of Ormond

The name never left its homeland. In 1851 there were more than a hundred Gleeson households in the civil parish of Kilmore alone, in the Silvermines hills south of Nenagh. Their nearest neighbours were the Hogans of Ardcrony and the O’Mearas of Toomevara. Both families, like the Kennedys who held the country around them, have a stronger claim to Dál gCais descent.

The family also produced the historian who wrote much of Ormond’s story. Dermot F. Gleeson’s books and journal papers on the castles, churches and freeholders of north Tipperary, including The Last Lords of Ormond, are still the starting point for anyone researching the area.

Gleeson DNA and the Dál gCais

The Gleeson DNA Project sorts tested men into separate lineages, and they don’t all share one ancestor. One group, Lineage III, has its roots in County Clare and its terminal SNP is L226, the marker associated with the Dál gCais surnames. So some Gleeson men do descend from Brian Boru’s kindred in the male line, even though the surname tradition says otherwise.

The only way to find out which Gleeson family you belong to is a Y-DNA test. A Y-37 test from Family Tree DNA shows whether your paternal line fits the R-L226 pattern, and Big Y-700 places you on a precise branch. Women, or anyone tracing a Gleeson grandmother, should take Family Tree DNA’s Family Finder, which matches living cousins on every line. Our DNA guide explains how to read the results.

Gleeson places to visit

  • Nenagh: the heart of Gleeson country, with a 13th-century castle keep and a heritage centre. See places to stay in Nenagh.
  • Kilmore and the Silvermines: the old graveyard at Kilmore is full of Gleeson headstones.
  • Lough Derg: Dromineer harbour is 15 minutes from Nenagh, and you can see the Arra shoreline from the water by hiring a cruiser on Lough Derg.
  • Killaloe: Brian Boru’s royal centre, across the bridge from Arra. Plan it with our Brian Boru trail.

Related surnames

See the O’Mearas, Kennedys, Hogans and Hurleys, or browse all Brian Boru kindred surnames.

Frequently asked questions

Is Gleeson an Irish name?

Yes. Gleeson is the anglicised form of the Irish Ó Glasáin or Ó Gliasáin, and it is most common in Tipperary. Gleason is the usual spelling in the United States.

Are the Gleesons related to Brian Boru?

Not by the traditional pedigrees, which place them among the Aradh. But one Gleeson DNA lineage from County Clare carries R-L226, the Dál gCais marker, so some Gleeson men are Brian Boru’s kindred in the male line.

Where is the Gleeson family from?

Lower Ormond and Arra in north Tipperary, around Nenagh and the eastern shore of Lough Derg.

What does the name Gleeson mean?

It means “descendant of Glasán”, a diminutive of glas, the Irish word for grey or green.

Sources

  1. Maurice Gleeson, The Gleeson name in surname dictionaries, Gleeson DNA Project (quoting Woulfe and MacLysaght).
  2. Maurice Gleeson, The origins of Lineage III Gleesons, Gleeson DNA Project.