Salmon of Knowledge

A magical fish which lived in a pool on the Boyne: whoever ate the salmon would gain all the knowledge in the world. The poet Finn Eces (Finneces, Finegas, Finnegas) -- under whom the young Fionn mac Cumhail studied -- had spent seven years trying to catch the salmon. Eventually he did, and told the boy to cook it for him. While cooking it Fionn burned his thumb, and instinctively put his thumb in his mouth, swallowing a piece of the salmon's skin. This imbued him with the salmon's wisdom. He then knew how to gain revenge against Goll, and in subsequent stories was able to call on the knowledge of the salmon by sucking his thumb.