The Giant is an antagonist in the story of Finn MacCumhail, the Irish hero. This Giant appears halfway through the story, after Finn has escaped King MacArt's men and after his grandmother has sacrificed herself. Finn shelters in a cave, and waits awhile before in comes the Giant with a salmon in his hand. He is initially friendly and tells Finn to watch the salmon because he has chased it for three whole days and it is precious to him. The Giant seeks to possess the supernatural knowledge in the salmon. Finn finds this out when he accidentally burns himself on the salmon when he makes a blister form, so he pops the blister, but it burns his thumb right down so he gnaws on it, and immediately the salmon juice gives him the knowledge of all things. So Finn knows the Giant is evil and is after the knowledge he now has.  

Each time the Giant snores, when he snores in, his goat herd and Finn are drawn almost into his mouth - and when he snores out it is in reverse. But when Finn bites his thumb he knows what to do from the supernatural knowledge, and he takes his sword and shoves it in the Giant's single eye, blinding him.

But this Giant isn't giving in, and so he sits up and roars that Finn is as good as dead. He sits down in the doorway of the cave but Finn escapes by clinging under a goat as they are let out.

The Giant realizes Finn is out but instead of admitting defeat he places a tracking device on him by giving him a ring as a gift. This ring, once on Finn's finger, calls out to the Giant where Finn is. Finn has to run away repeatedly from the Giant's pursuit, where he hopes to crush Finn dead. But Finn's companion, the dog Bran runs up to him and asks him to bite his thumb to get the knowledge and once he does so, he cuts off his finger with the ring on it. He throws it into a swamp, and the Giant asks where it is. The ring answers, and the Giant throws himself into the swamp, and remains stuck there.