the custom of carrying the image of a boar upon one's helmet. The head contained the life and life-soul so that men who defended themselves were said to 'guard their heads'. The helmet or 'head-protector' (heafodbeorg) is referred to simply as 'the boar'.
Onians argues that the Germanic helmet is a theological instrument: bearing the boar-emblem of Freyr, it protects the life-soul housed in the head, collapsing the distinction between armor and sacred guardian.
, The origins of European thought about the body, the mind,, 1988thesis