Surnames beginning in "Mc" and "Mac"... Irish or Scottish?

[Graham]

I have heard that surnames beginning in "Mc" are Irish and those beginning in "Mac" are Scottish. Is this true?

No, Scots can have both Mc & Mac. But Ireland rarely has Mac, perhaps only in Ulster. Ireland has O' unlike Scotland.

Ni or Nic is the female version(daughter of) in proper Gaelic names.

[Graham]

Sorry to revive an old thread, but I have a question regarding "Mc" and "Mac" surnames:

If I were to ask someone with a "Mc" or "Mac" surname the initial letter of their surname, is it true that the "Mc/Mac" is not taken into account, e.g., someone with the surname McBride; the first initial would be B.

I'm no expert on this subject matter, but I'm interested if this is indeed the case or not and if so, why?

I would assume that people with Mc/Mac surnames would say the first letter is M, whereas someone I spoke to recently has told me otherwise. It's the first I've heard of this and I'd like to know if there's any truth to it. Is there a cultural or other reason for doing so?

Likely in the Gaeltacht. Considering son of has its proper meaning.