What is "nebelung"

The Nebelung is a rare breed of domestic cat. Nebelungs have long bodies, wide-set green eyes, long and dense fur, and mild dispositions. The name Nebelung — apparently a portmanteau of the German word Nebel ('mist' or 'fog'), and the name of a medieval Germanic saga, Nibelungenlied — is perhaps derived from the cat's distinctive silky blue-grey coat and from the breed's progenitors, who were named after the two major figures in the Nibelungenlied, the German warrior Siegfried and the Icelandic queen Brunhilde.