The Salmon of Knowledge:
According to Irish Mythology it was an ordinary salmon that ate the nine hazelnuts that fell into the Fountain of Wisdom from the nine hazelnut trees, that surrounded the fountain. From the Fountain of Wisdom five rivers flowed out including the River Boyne and the River Shannon. After eating the nine hazelnuts, the salmon gained all the knowledge in the world. The first person to eat its flesh would in turn gain all of this knowledge.

The salmon was caught by Finegas, a poet and teacher of many years.While his apprentice Fionn Mac Cumhaill was cooking the great fish, Fionn burned his thumb on the flesh of the salmon and immediately sucking his thumb to ease the pain, fulfilled the ancient prophecy, that he who first tastes the Salmon of Knowledge would posess all the knowledge his mind can hold. It was this great knowledge and wisdom gained from the Salmon of Knowledge that allowed Fionn to become Leader of the Fianna, the famed heroes of Irish Mythology.