These rivers are mentioned in verse 29 of the Grimnismol:
Kormt and Ormt and the Kerlaugs twain
Shall Thor each day wade through,
When dooms to give he forth shall go
To the ash-tree Yggdrasil;
For heaven's bridge burns all in flame,
And the sacred waters seethe.
There are 2 prevailing interpretations of this verse:
the verse ...