Well, it's a very old-fashioned name. It doesn't sound like a grandfather name. It's more of a great-grandfather name. It would sound very pompous and pretentious, not to mention plain ridiculous, on a child today. I'm not German, but I do know something about German culture as a German student. Of course, the real reason I hate this name is that it can only really be associated with that sexist man Freud, who had the audacity to talk about female sexuality as if women were like children or pets who couldn't speak for themselves and say asinine things about it as if he even COULD have known what he was talking about.
This seems like a good, strong name. It sounds like a hero in a fantasy book. I also like the nicknames of "Sig" or "Siggie" that you could turn it into.