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Parent’s name

Reilly surname meaning

An Irish patronymic from Ó Raghailligh, “descendant of Raghailleach,” a personal name of uncertain etymology; the Cavan chieftain family.

Confidence
High
US frequency
Rank 853 · 39,645 people
Common variants
Reilly, O'Reilly, Riley, Rielly, Rahilly

The short story

Reilly is an Irish surname from Gaelic Ó Raghailligh, “descendant of Raghailleach” (Old Irish Roghallach), a personal name whose exact meaning is unexplained. It belongs to a major Breifne chieftain family centered in County Cavan and related to the O’Rourkes; the Anglicized form O’Reilly is the same name with the Ó kept. Riley, Rielly, and Rahilly are historical spellings, and Munster Ó Raithile (O’Rahilly) has sometimes been confused with it. Parent’s name is high confidence: the surname is a classic Irish patronymic from a known medieval personal name and clan.

Also seen as: Reilly, O'Reilly, Riley, Rielly, Rahilly

Sources used
  • Ancestry / DAFN entry for O’Reilly (Ó Raghailligh, descendant of Raghailleach; Cavan)
  • Ancestry / DAFN entry for Reilly (from Ó Raghailligh)
  • Wikipedia “Reilly (surname)” (Ó Raghallaigh; Cavan/Westmeath)
  • Names2020_LastNames_RaceHispanic_Top1000.xlsx (2020 Census)