“Hereward must have been a famous man when he took his stand in the fens of Ely. That his biographers explains his fame by the application of ancient traditions is only saying that his countrymen reckoned his fame as of the very highest; ordinary current events of the day would not suit their ideas of the fitness of things. Hereward was as Alfred had been, as Arthur had been, and so he must have his share of the national tradition, even as these heroes had. To say less of him was to have put him below the others."
and so it must have been about the original heroes of the sagas. One other problem with the Nibelungenlied is that some of the characters are cowardly and treacherous and the people who they represent may still have powerful descendants. So, do you give their names? Most likely, if you want to live, you do like Procopius, you compose your history full of accolades and save the truth for posthumous publication.
The Nibelungs were, at the beginning of the story, called the Burgundians but, as the story progresses and they take possession of the treasure, that Siegfried had won from the original Nibelungs, they take on the name as well as the curse that goes with the treasure. I think the hoard was the treasure taken from Rome when it was sacked by Alaric. He died soon after and was buried in the Busento River, which had been diverted for the purpose and the slaves who performed the work were killed so no one would find his grave(according to Jordanes). The entire treasure was not buried with him but his successor Athavulf, Alaric's brother in law and member of the Balti (a royal clan exceeded in prestige only by the Amali), went back to Rome to loot it again and fell in love with a royal hostage Galla Placidia, sister of the Roman emperor, whom he had seized and taken with him. Honorius was not happy when Athavulf married Placidia but he was powerless to prevent it. Placidia, for her part, does not seem to mind Athavulf, who gave her the hoard taken from Rome as a wedding gift, at all. Jordanes describes him thus:
"a man of imposing beauty and great spirit; for though not tall of stature, he was distinguished for beauty of face and form" A fighting man, descent from royal Germanic clan, leader of his tribe and good looking too, sounds like Siegfried to me. Arcadius and Honorius, her brothers considered it a shameful alliance. Placidia's one somewhat questionable act was to vote in favor of the execution of her cousin Serena, who had been married to Stilicho, and who had robbed a statue of Rhea of its beautiful necklace and liked to parade about in it. Serena had been accused of conspiring with Alaric to bring down the empire. She was not guilty but after Honorius had Stilicho murdered almost everyone attached to him was killed. So we clearly have treachery and murder, vital ingredients to the Nibelung plot but we are missing revenge and blood feuds
There was another Goth, one of the Amali, who was working also for Honorius, who was a rival to Stilicho, called Sarus. He attacked Alaric as Alaric was going to negotiations with Honorius. This was the act that caused Alaric to sack Rome in 410. Later Athavulf waylaid Sarus as he was travelling to Gaul to join Jovinus and and Sarus was killed. Athavulf, for some incredible reason, took in one of Sarus' followers into his service. That man, Evervulf, stabbed him in the groin and killed him. Zosimus wrote that Evervulf did this while Athavulf was taking a bath. Sarus' brother Segeric took control of the Visigoths but he was killed in revenge for the death of Athavulf seven days later. After that Walia became king of the Visigoths. He returned Placidia to her brother Honorius and became an ally to the Romans for which he was given Aquitaine where he ruled in Toulouse for many years and may be the man known as Walthar of Aquitaine.
Placidia = Grimhilda? Maybe, if you throw in the story of her daughter Honoria, who had been kept in a convent by her brother, Valentinian, who ruled after Honorius. Valentinian feared plots by Honoria for his throne. Honoria had sent a servant with a plea and a ring to Attila the Hun to liberate her. Attila took this as a marriage proposal and marched on Rome to claim his bride and her dowry. He was stopped by Aetius in the Battle of the Catalaunian Plains. Aetius, like Hagan, had been a hostage at Attila's court when growing up. I hate to say Aetius is Hagan because Hagan is a treacherous and dark character where Aetius was a man of honor who was treacherously slain by his leader but I think Hagan is one of the older supernatural elements of the story like the dragon.
Attila then heads for Rome but, being superstitious, he remembers what happened to Alaric after he sacked Rome (he died) and he turns to Ravenna. Pope Leo is able to persuade him to leave but, after rampaging through the swamps around Aquiliea and catching who knows what diseases, the Huns were ready to go home anyway. Attila died not long after but another hostage or member of his court is the king of the Ostrogoths Valamir and his two brothers Vidimer and Thuidimer. They decide to free themselves and their people upon the death of Attila and while the fight was on, Thuidimer became a dad to Theodoric the Great. Theodoric was held as a hostage at the Byzantine court for a while, which is where his wild glory seeking Germanic ways were tempered by the court.
So then, what happened to the treasure? Walia did not give that back with Placidia; the Visigoths kept that. Walia did fight some fighting against Gundahar, who was King of the Burgundians and tried to assist the Roman usurper Jovinus. Gundahar is one candidate for the historical Gunther but in the second Burgundian kingdom. The first kingdom was closer to Worms, their legendary capital, but they were wiped out by Aetius with the aid of Hunnish mercenaries. Aetius allowed the remaining Burgundians to settle in Gaul but further west, they were included in the federation that halted Attila's advance across Europe. After some serious infighting and kinslaying, they were absorbed into the Frankish kingdom of Clovis who married the Burgundian Clotilde. Clovis' sister married Theodoric the Great and we come full circle to where they are all related now. Clovis attacked the Visigoths for the treasure and he got what was left of it.
From Clovis, we get the famous rivalry of Brunhilde and Fredegunde, Sigismund, Gundobad and other potential candidates for Nibelung characters but never mind. In the end, the Germanic peoples become the Romans. They joined the empire. Their leaders ruled Italy, their king became the Holy Roman Emperor. The Burgundians became the Nibelungs, get it?