Grottisöngr is a Scandinavian legend that was written down by Snorri Sturluson in the Poetic Edda. It warns against greed and explains why the sea turned salt. It has also survived independently as a heavily modified Scandinavian folk tale. It has been used as a political metaphor by Scandinavian socialists.

Skjöld was a son of Odin's and he was the ancestor of the Skjöldungar (Scyldings). He ruled the country that we today call Denmark. Skjold had a son named Fridleif and who succeeded him on the throne. Fridleif had a son who was named Fródi who became king after Fridleif at the time when Caesar Augustus proclaimed peace on earth and Christ was born. The same peace ruled in Scandinavia and it was called the Fródi peace when no man hurt another, even if he met his father's or his brother's killer, free or tied. No man was a robber and a golden ring could rest on the moor of Jalangr for a long time.

King Fródi visited Sweden and its king Fjölnir. Then he bought two female slave Jotuns named Fenja and Menja who were big and strong. At the time there were two big mill stones in Denmark that were so big that no man was strong enough to use them. However, the man who ground them could ask them to produce anything he wished. This mill was called "Grotte" and it was given to Fródi by Hengikjopt.

Frode had Fenja and Menja tied to the mill and asked them to grind gold, peace and happiness for Fródi. Then he gave them neither rest nor sleep longer than the time of a song or the silence of the cuckoo. In revenge Fenja and Menja started to sing a song named the "song of Grotte" and before they ended it, they had produced a host which had a sea-king named Mysing who attacked Fródi during the night and killed him. The host left with rich booty.

That was the end of the Fródi peace.

Mysing brought Grotte as well as Fenja and Menja and asked them to grind salt. At midnight, they asked Mysing if he did not have salt enough, but he asked them to grind more. They only ground for a short while before the ships sunk. A whirlpool was formed and it went through the centre of the mill stone. Then the sea turned salt.