Reilly
An Irish surname, usually from O’Reilly, meaning a descendant of an early Irish ancestor name.
The #845 most common surname in the United States (2010 Census) — about 1 in every 7,552 Americans shares it.
Etymology
Reilly is the Anglicized form of the Irish surname O’Reilly, from Gaelic Ua Raghallaigh, meaning “descendant of Raghallach.” The older personal name is traditionally linked to a Gaelic byname or ancestor-name, though 19th-century sources vary a little in how they spell and analyze it. In practice, the surname developed as a clan name in Ireland and then lost the O’ in many records and emigrant families.
History
The Reilly name is strongly associated with Irish history, especially the old O’Reilly dynasty of County Cavan and the wider Breifne region. English-language records often shortened O’Reilly to Reilly, Riley, or related forms, especially in Britain and the United States. This spelling became common enough that later surname books treated Reilly and O’Reilly as the same family name in origin.
Origin
Regions
Variant spellings
Fun fact
In some 19th-century surname lists, Reilly was noted as one of the more common Irish names surviving after many O’- prefixes were dropped in Anglicized records.
From the historical record
“REILLEY^ REILLY REILY RELLY for O'Reilly, q.v. RELF RELFE”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)Notable people named Reilly
- John C. Reilly (b. 1965)
Sourced from Wikidata; linked to their Wikipedia page.