O'Reilly


O'Reilly is a group of families, ultimately all of Irish Gaelic origin, who were historically the kings of East Bréifne in what is today County Cavan. The clan were part of the Connachta's Uí Briúin Bréifne kindred and were closely related to the Ó Ruairc of West Bréifne. O'Reilly is ranked tenth in the top twenty list of most common Irish surnames.
It is also the patronymic form of the Irish name Reilly. It is commonly found throughout Ireland, with the greatest concentration of the surname found in County Cavan followed by Longford, Meath, Westmeath, Fermanagh and Monaghan, and the Province of Leinster.

Naming conventions

MaleDaughterWife 'Wife '
Ó RaghallaighNí RaghallaighBean Uí RaghallaighUí Raghallaigh

Overview

It is usually anglicised as Reilly and O'Reilly. The original form of the name, Ó Raghallaigh, denotes "from/of Raghallach", the name Raghallach thought to be derived from the compounds ragh and ceallach.
The Ó Raghallaigh family were part of the Connachta, with the :wikt:eponym|eponymous Raghallach said to have died at the Battle of Clontarf in 1014. The family became the kings of East Breifne, modern-day County Cavan and County Longford.
The name is common and widespread throughout Ireland, ranked 11th most common in 1890 and in 1997.
The O'Reilly Clan Chieftain to this day is at odds with the O'Rourke Clan Chieftain because both clans viciously contest each other for the title Prince of Breifne. This was settled in 1994 when the Chief Herald of Ireland made the O'Rourke Chief the Prince of Breifne, but the Office of the Chief Herald stopped granting courtesy titles to Gaelic Chiefs in 2003. In 2017, with the election of the new O'Reilly Chief, the rivalry has been rekindled.

People

O'Reilly

People with the surname O'Reilly include:

Fictional people