13th century, Icelandic: numerous copies in Iceland, Copenhagen.
'During the day he often changed himself into a salmon and hid in a place called Franang's Falls.'
Then Gangleri said, 'Loki was the cause of many things… But was no vengeance taken for this?'
High replied: '… With the gods as angry at him as might be expected, he ran away and hid on a mountain. There he built a house with four doors, so that he could look out from the house in all directions. During the day he often changed himself into a salmon and hid in a place called Franang's Falls.'
Story fragment quoted from: Byock, Jesse L, 2005. Snorri Sturluson: The Prose Edda, Norse Mythology, translated from Old Norse with an introduction. Penguin Books Limited. Gylfaginning, 50. Loki is caught and the Aesir take Vengeance, p 69.
Snorri Sturluson – Wikipedia
Prose Edda (Younger Edda) – Wikipedia
Elder Edda and Younger Edda – Project Gutenberg; free out-of-copyright editions, ebooks