What does the "O" mean in an Irish name?

A man told me a while back that if you had the name O'Byrn or O'Neil or O'Keller it simply mean that you belonged to the "clan of" Keller or the Clan of Byrn or the Clan of Neil. I recently read online, however, that it means "descendant of" or "son of" so I'm a little confused. Which one is more accurate or are they both accurate?





It's intriguing to me because when I was around 27 years old my wife figured out that my dad wasn't my biological father. Ever since I've always wondered who my biological father was and what his real name was ( mom %26amp; dad were no help...this is Jerry Springer stuff trust me.. uggh ).





So one day a guy saw my last name O'xxxxx and says, "you a little Irish are ya?" I said, "well..not really sure if I am to be honest," and then I laughed and shared my story. That's when he explained that I was still an O'xxxxx because I had been accepted into the "Clan" of xxxxx so the name was still mine.





Thanks in advance for thoughts!

What does the "O" mean in an Irish name?
I have just found out that it means the son of or descendant so both are an accurate description. Hope this is okay for you Knell 22
Reply:I think (taking a guess here) that it was Of in another time.





Like John O' Laughlin might have been John OF Laughlin, which could be John OF THE Laughlin family or John OF the town of Laughlin, which is probably what led to the Laughlin family in the first place.





That's a guess, though. I'm gonna have to check back now, to see if I was close.
Reply:Its like a family clan name, Germans use von, scots use mac and headhunters use anak.
Reply:O' means descendant of. Some say grandson of.





Mac,Mc,Fitz means son of.
Reply:"Son of"





Like "Ap" in Welsh (not very commonly used anymore)
Reply:"o" means Of, like the sone of Brian so it would be Tom O'Brian.

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