Your friend is mistaken. I have done a bit of historical onomastic (name origin) research, and spoken with folks who have doctoraates or equvalents in the subject.
both Irish and Scottish Gaelic use O', Mac, and Mc. The difference between Mac and Mc is only of usage--it arose before spellling was standardized, when names were writtend own phonetically by scribes who half the time did not even speak the language. The difference between O and Mac/Mc is of meaning. O'Dammit is a member of the family of Dammit, named after an illustrious ancestor named Dammit, who himself might have been Dammit O'Darn or Dammit McGosh, frex. McDammit (or Mac Dammit) is the son of Dammit himself--or a descendent of the son of Dammit, after the point at which surnames switched from being literal to inherited. Before around 1400, there were no female Mc Anythings; the equivalent for a woman was 'ingen', spelled variously, meaning "daughter of".
no subject
I have done a bit of historical onomastic (name origin) research, and spoken with folks who have doctoraates or equvalents in the subject.
both Irish and Scottish Gaelic use O', Mac, and Mc. The difference between Mac and Mc is only of usage--it arose before spellling was standardized, when names were writtend own phonetically by scribes who half the time did not even speak the language. The difference between O and Mac/Mc is of meaning. O'Dammit is a member of the family of Dammit, named after an illustrious ancestor named Dammit, who himself might have been Dammit O'Darn or Dammit McGosh, frex. McDammit (or Mac Dammit) is the son of Dammit himself--or a descendent of the son of Dammit, after the point at which surnames switched from being literal to inherited. Before around 1400, there were no female Mc Anythings; the equivalent for a woman was 'ingen', spelled variously, meaning "daughter of".
Clear as mud?