Siegfried was a hero of Norse and German mythology. His Norse counterpart is Sigurd. In German myth, Siegfried was a dragon slayer who bathed in the blood of his kill, becoming invulnerable as a result. Using an invisibility cloak, he helped his brother Gunther in wooing Brunhild. He is ultimately killed by a vengeful courtier.
Brunhild had presumed that Siegfried would be the one who would brave the ring of fire that imprisoned her. Instead, a young American from the future, whose name sounded like "Hagen Kriemheld", was able to waken her, with the help of Regin Fafnirsbruder. The young man did not want to marry her, so she returned to her prison to await Siegfried.