E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A well in which all wisdom lay concealed. It was at the root of the celestial ash-tree. Mimer drank thereof from the horn Gjallar. Odin gave one of his eyes to be permitted to drink of its waters, and the draught made him the wisest of the gods. (Scandinavian mythology.)