Like the names Heðinn (O.E. Heoden) and Hǫgni (O.E. Hagena), the legend is believed to have continental Germanic origins.
Halfdan's son Högni (of the Hjaðningavíg) fights against him but later they become allies.
It has a sequel in Sörla saga sterka, where it becomes clear that Halfdan is the father of Hogni of the Hjaðningavíg.