help! confused about last name

Hey there. I have a quick question for you guys. I was just wondering about my last name, Rudenberg. My Grandfather, Francis Rudenberg, is a full-blooded Norwegian. But the name itself is odd to me. Sounds more German than Norwegian, doesn't it? Rumor has it that the family changed the name from something else around the 1820s (?). But, unfortunately, information about that sort of thing is hard to come by, Can anyone tell me if Rudenberg is even a remotely Norwegian name? I would really like to know. Thanks a bunch.