mythology
What I suspect but am not sure is that we’re seeing a relatively late and modernized gloss of vital folk beliefs, and that what people practiced in the 300s-400s when these bigger kingdoms come along, was different from what had evolved by the time of the Viking Age, and that Snorri and others are a further refinement of those later beliefs. I have some UPG about the myth of the Fenris Wolf which relates to that one.