Bradán feasa is a creature figuring in the Fenian Cycle of Irish lore; not to be confused with the Fintan mac Bóchra, who was known as "The Wise" and was once transformed into a salmon.
The Salmon figures prominently in The Boyhood Deeds of Fionn, which recounts the early adventures of Fionn mac Cumhaill.
According to the story, it was an ordinary salmon that ate the nine hazel nuts that fell into the Well of Wisdom (aka Tobar Segais) from nine hazel trees that surrounded the well.
In doing so, the salmon gained all the knowledge in the world. Moreover, the first person to eat of its flesh would, in turn, gain this knowledge.
The poet Finn Eces spent seven years fishing for the salmon. When he finally caught it, he instructed his apprentice, Fionn, to prepare it for him.
Fionn burned his thumb when spattered with a drop of the hot fat from the cooking salmon and immediately sucked on it to ease the pain. Unbeknownst to Fionn, all the wisdom had been concentrated into that one drop, and Fionn had just imbibed it all.
When he brought the cooked meal to Finegas, his master saw a fire in the boy's eyes that had not been there before. When asked by Finegas, Fionn first denied that he had eaten of the fish. But when pressed, Fionn admitted his accidental taste.
Throughout the rest of his life, Fionn could access this font of knowledge merely by biting his thumb.
It was this incredible knowledge and wisdom gained from the Salmon of Knowledge that allowed Fionn to become the leader of the Fianna, the famed heroes of Irish folklore.
In Welsh lore, the story of how the poet Taliesin received his wisdom follows a similar pattern...
Similarly the legendary Welsh poet Taliesin claims:
"I have been a blue salmon
I have been a dog
I have been a stag
I have been a roebuck on the mountain
I have been a grain discovered....
I rested nine nights
in her womb, a child
I have been dead, I have been alive.
I am Taliesin...
A very ancient salmon features in the Welsh tale, Culhwch and Olwen, an early Arthurian legend.
Culhwch is given a series of near-impossible tasks by his prospective father-in law, before he can win the hand of his beloved Olwen.
One of the tasks is to find and release Mabon, a divine child who has been imprisoned. After asking a series of wise old beasts, none of whom know the child's whereabouts, Culhwch and Arthur's men are directed to the oldest and wisest of the animals, the Salmon of Llyn Llyw.
The salmon not only tells them where Mabon is, but kindly (and impressively) gives them all a ride on its back to the prison, where they succeed in their mission...
Resources:
Post Image: http://bit.ly/167A0Dn
Mhd.Shadi Khudr's insight:
"[The Druid renames him Fionn, for the glow of inspiration.]"
http://bit.ly/12TEf8b