it ' s just understood we ' re talking about our descent or heritage . Even then it ' s still flawed . You might have had a g reatgreatgreatgrandparent from Norway , but even making the giant assumption that he himself was 100 % Norwegian , the bloodline will have been mixed with people from all over during the last century or so in the USA . You might say you ' re Lithuanian for example , but presumably that ' s just passed down information and attachment through the generations from the original guy who was from that country , in reality the Lithunian part has likely been mixed down to a very insignificant part of your makeup by now , and you ' re might be more Irish or some other random thing that you never thought . People usually follow the father ' s side where the surname comes from and say that ' s what they are , while not paying attention to generations of mother ' s who had equal contribution to genetic makeup all along the way . Suffice to say it doesn ' t make much sense to me .