McDonald Mcadams McCarthy mcconaughey mclean mcgregor mclntous surnames starting with mac or mc but they raise the question:why is the prefix mac or mc so commonly found among us? These surnames actually originated among the Scottish and the lrish. Mac and its abbreviation,mc are prefixes meaning 'son of' areusually followed by the name of ancestors. For example, the mcdonald surname originally refers to the 'son of donald'. Mc and mac are sometimes followed by tge father's professsion'such as macmaster'or some physical feature of the person, such as mackenzie meaning son of the fair one.