"The Swollen", "The Roaring." The river that surrounds Valhalla, mentioned in the eddic poem Grímnismál:
- Thund roars;
- joyful in Thiodvitnir's
- water lives the fish;
- the rapid river
- seems too great
- for the battle-steed to ford.
The fish in Þióðvitnir's water is presumably the sun, caught by the wolf Sköll, Þióðvitnir meaning "the mighty wolf."
- Grímnismál, 21.