I had never heard of Kennings before I joined Mello-Elo and her group for Monday Coffee this morning, so please excuse my amateurish first attempt. It is a riddle. When you’ve guessed what it is, please hop across time and space to her sitting room, enjoy the coffee and see my answer in the comments. Just follow the link.
As I said, just follow the link for a coffee and the answer.
That was fun!