Thorism

In the lands of northern Europe, this pantheon of gods, the Aesir, were worshipped. Chief among them Thor, the God of Thunder. They are still worshipped to this day.

Hler says that once upon a time "Balder and other Norse gods were merely powerful tribal leaders."

It's very possible that some of these gods were imported into Novgorod and Kiev and their names changed. For example, Perun, from Kievanism, is very similar to Thor in most respects.