In the story, an ordinary salmon ate nine hazelnuts that fell into the Well of Wisdom (an Tobar Segais) from nine hazel trees that surrounded the well.

Finally Finn caught the salmon and gave the fish to Fionn, his servant and son of Cumhaill, with instructions to cook it but on no account eat any of it.

[2][3] In Irish mythology, several primordial beings that personify old age and ancient knowledge are described as taking the shape of a salmon.

[5] In the Icelandic Völsunga saga (late 13th century), these motifs also recur: Odin, Loki, and Hœnir slew an otter that they later found to be Ótr, the son of the dwarf Hreiðmarr.

[6] Similarly, Saxo Grammaticus (Gesta Danorum, V.2.6-V.2.8, 12th c.) describes how Eric acquired eloquence and wisdom by eating the snake-infested stew his step-mother Kraka had prepared for his half-brother Roller.

In 2019, the Dublin-based Gilla Band released "The Salmon of Knowledge" on their album The Talkies, which takes its title and some thematic content from the folk tale.