He burnt his thumb trying to turn the wise fish FINTAN on a makeshift spit, and when he sucked the resulting blister a great splurge of knowledge was released into his head. But his digestive system couldn’t cope and all the knowledge passed onto his son OISIN.
With a salmon that smart, it’s more than likely it escaped back into the river and burning Finn with a fin was a ruse to put this into effect.
The heroic FIONN-MAC-CUMHAILL delights in cross-country running into strange situations with dogged persistence.
He is so popular that there is even a spin-off giant character called FINN-MACCOOL.