i.e. Attila. King of the Huns, a monarch ruling over three kingdoms and more than thirty principalities; being a widower, he married Kriemhild, the widow of Siegfried. In the Nibelungen-Lied, where he is introduced (part ii.), he is made very insignificant, and sees his liegemen, and even his son and heir, struck down without any effort to save them, or avenge their destruction. He is as unlike the Attila of history as possible.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894