Hati & Skoll.

The Wolves.

"Sun always seems to be in a great hurry, and that is because she is chased by Skoll, the wolf who is always snapping and growling close behind her. In the end he will catch her. And the wolf that races in from of Sun is called Hati; he is after the Moon and will run him down in the end."

From: The Penguin Book of Norse Myths - Gods of the Vikings.
~ Kevin Crossley-Holland.

That somewhat circular notion was the inspiration for this design.