Salmon of Knowledge pendant on 18″ chain in sterling silver. Legend: Finn MacCool is a mythological warrior that appears in several Irish legends. One popular story tells of a salmon that knew all of the world’s knowledge. Finn decided to eat the Salmon to gain the knowledge. As he was cooking the fish, he reached to touch it and burned his thumb. Finn stuck his thumb in his mouth to stop the pain and instantly learned the knowledge the salmon carried. From then on, anytime Finn sucked his thumb he gained whatever knowledge he was seeking.