What does the O in Irish names mean?

Others used family names. O' means grandson of (not son of, as it commonly believed). So the name O'Connor would mean "Grandson of Connor." The prefix O' is almost always Irish. Mac or Mc means son of. My [married] last name "McDowell" means "son of Dowell." McDowell is Scottish, but in general, Mc and Mac could be either Irish or Scottish. read more

A formal Irish-language personal name consists of a given name and a surname. Surnames in Irish are generally patronymic in etymology, although they are no longer literal patronyms, as Icelandic names are. read more

The prefix O' seen in Irish surnames is from the Irish (Gaelic) Ó (earlier Ua) which means 'grandson, descendant'. O'Neill in Irish is Ó Néill (descendant of Niall). Grandson or descendant. read more