O'Neill surname meaning

O'Neill, usually written O’Neill or Ó Néill, is an Irish patronymic surname meaning “descendant of Niall.” The older form Ua Néill identifies descent from a man named Niall, and the name is historically associated with Ulster and Tír Eoghain. Niall is often glossed “champion” or “warrior,” but that traditional interpretation belongs to the personal name rather than to every O’Neill family. Apostrophe and accent loss is routine in Census and immigration records. The catalog uses parent’s name with high confidence because the Gaelic descendant formation is direct, while separate O’Neill lines could have formed from different Niall ancestors.