Quoting Mayhem ♥:" I mean...isn't it a last name? In which case it'd be either gender"
Surnames are masculine - I know a lot of people USE them on girls, but they are traditionally masculine because it's the family name and with the exception of VERY few cultures, most were patriarchal, so the family name would be passed down through the son and often contain the father's or patriarch of the family's name. This name originated as Irish and then was Anglicized into English in it's present form, but it's original meaning is "descendant of Proinnteach",
Proinnteach being the male patriarch.