Finn MacCool and the Salmon of Knowledge.

The eo fis, the Salmon of Knowledge, acquired its supernatural wisdom through eating the nuts of 9 hazel trees which fell into the Well of Seghais, the spring of the otherworld in which it lived, and made bubbles of inspiration.

Finn (or Demhne to give him his true name) went to seek instruction from Finn the Poet. Finn the Poet had been waiting seven years for the Salmon of Linn Feii, because it was prophesised that eating the salmon would bring him boundless knowledge. The salmon was caught and entrusted to Demhne to cook; but the poet told him not to eat any of it. When Demhne brought him the cooked salmon, he told the poet that he had not eaten any of it but described how he had burnt his thumb on the salmon and then put his thumb in his mouth. The poet said that Demhne would from then on be known as Finn, and that he should eat the flesh of the salmon. In doing so, Finn learned the three qualifications of a poet:- that is, "knowledge that enlightens", "chewing the pith" and "incantation from tips". Whenever, in the future, Finn MacCool put his thumb in his mouth and sang "chewing of the pith", whatever he didnt know was revealed to him.