Donar (Scand.), or Thunar, Thor. In the North the God of Thunder. He was the Jupiter Tonans of Scandinavia. Like as the oak was devoted to Jupiter so was it sacred to Thor, and his altars were over shadowed with oak trees. Thor, or Donar, was the offspring of Odin, “the omnipotent God of Heaven”, and of Mother Earth.
Source: H.P.Blavatsky - The Theosophical Glossary