Appearing in the Volsung Saga, this seems to have been a literal reference to a helmet however, in Icelandic tradition, the Helm of Awe, or Aegishjalmarr, features in various Germanic holy art as an 8 pointed star-type drawing. Throughout the same era, the symbol was drawn between the eyes of warriors in order to give them great strength and to terrify their opponents.
The Helm was found amongst the horde stolen by the god Loki in order to pay weregild for the death of Otter, brother of Fadhmir. Fadhmir donned the helm as well as several other pieces of armour and eventually became the dragon guarding the horde.