The following is from a "tracing your Scottish ancestors" web site.
The prefix "Mac" means "son of" in Gaelic. Until the 16th Century, individuals in Gaelic-speaking Scotland were given only one name and thus were referred to as Duncan, son of Donald. It was only later that this convention was used to form a formal surname. Mac is variously rendered as Mc or M'. The suggestion that names beginning "Mc" are Irish and "Mac" are Scottish is wrong. Within Gaelic, "Nic" is the female equivalent of "Mac", that is "daughter of". Thus a female's surname with the surname MacGovan, will appear in Gaelic as Nic Ghobhain, not Mac Ghobhain. However, Nic never appears in the anglicised version of a surname.
It looks as if Mac and it's variants can be Scottish or Irish.