E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The ash-tree, whose roots run in three directions: one to the Asa-gods in heaven, one to the Frostgiants, and the third to the under-world. Under each root is a fountain of wonderful virtues. In the tree, which drops honey, sit an eagle, a squirrel, and four stags. At the root lies the serpent Nithhöggr gnawing it, while the squirrel Ratatöskr runs up and down to sow strife between the eagle at the top and the serpent. (Scandinavian mythology.)