What do the beginnings of Irish last names mean?

Question:

What do the beginnings of Irish last names mean?

Like the "O", "Mc", and "Mac"?

Are they scottish as well?

Best Answer - Chosen by Asker: "O" means "descendant of", and "Mc" and "Mac" mean "son of".

"O" is not a characteristic prefix of names of Scottish origin, though it was used throughout the British Isles at one time, as testified by the town "John O'Groats", (founded by a Dutchman named John DeGroot).

The legendary English folk hero Robin Hood, not the least bit Scottish or Irish as far as I know, also was called Robert Of Locksley, and is likely to have been called "Robert O'Locksley" by some people, but in England "O" merely denoted the place people were from, not their ancestry.

The Scottish or Irish name "McDonald" indicates that the father's name was "Donald", but the Irish name "O'Sullivan" indicates that a man named Sullivan (Suil Ban, Gaelic for "Blue Eyes") was in the ancestral line somewhere, not necessarily the father. At least the American descendants of the Sullivans, the Donovans, and others usually drop the "O".

The legendary Irish folk hero and mythical giant slayer Finn McCool (Fionn Mac Cumhail) was the son of Cumhail, who, in turn, was the son of Trenmor. So Finn could with equal justice have called himself Finn O'Trenmor. ("Fionn" means fair of skin.)

It's irrelevant to your question, but fair skin and blue eyes are not now considered as unusual features of the Irish, and yet, among the swarthy, dark-eyed ancient Irish, these traits were unusual and distinctive enough to lead to people being named the Gaelic versions of the names "Blue Eyes" and "Fair Skin", which became the family names cited above.

These names evidently originated before massive Norse invasions and consequent Irish assimilation of the fair-haired, blue-eyed Norse genome.