Kennings
Kennings are metaphorical words or phrases. Common examples are various trees for people, "whale road" for oceans, "swan road" for a lakes, "sea horse" or "sea dragon" for a ship. Often, the metaphor is a little hard to understand at first, but becomes clear from its context. For instance, "battle tree" connotes a warrior, whereas "battle twig" is a sword or weapon of some kind.