Why was Poseidon angry with Odysseus?

The shout from the ship

Odysseus had already won. The giant was blind, the men were out of the cave and the flock was on board. As the ship pulled away he jeered once, and Polyphemus tore off a hilltop and hurled it; the wave nearly drove them back to shore. His crew begged him to keep quiet (Odyssey 9.494–499). He shouted again anyway, and this time he gave his name.

Cyclops, if any one asks you who it was that put your eye out and spoiled your beauty, say it was the valiant warrior Ulysses, son of Laertes, who lives in Ithaca.

Butler uses the Latin form of the name, Ulysses. Notice how complete the boast is: a name, a father, an island. The giant groans that an old prophecy has come true. A seer named Telemus once told him he would lose his sight to Odysseus, and he had always expected a giant, not a little nobody who beat him with wine (9.507–516).

The prayer, clause by clause

Then Polyphemus lifts his hands to the sky and prays to his father, using every part of the name he has just been given.

grant that Ulysses may never reach his home alive; or if he must get back to his friends at last, let him do so late and in sore plight after losing all his men

One more line, which Butler suspected was added later, ends the curse: on another man’s ship, and to trouble at home. Homer’s comment is brief, in Butler’s Roman name for Poseidon: “Neptune heard his prayer.” The rest of the Odyssey is the fulfilment.

• Late. He reaches Ithaca in the twentieth year after sailing for Troy, ten years after the war.
• Without his men. Twelve ships leave Troy, and the last crew dies after eating the cattle of the Sun.
• On another man’s ship. The Phaeacians carry him home asleep in one of theirs.
• Trouble in his house. He finds 108 suitors eating his flocks and courting Penelope.

Tiresias says it again

In the land of the dead, the prophet Tiresias opens with the same verdict: Poseidon nurses a grudge for the blinding of his son (11.100–103). Later he repeats the end of the curse almost word for word, late, wretched, alone, on a stranger’s ship, to a house full of men devouring his goods (11.113–117). He also gives the cure. After the suitors, Odysseus must carry an oar inland until a traveler mistakes it for a winnowing shovel, then plant it and sacrifice a ram, a bull and a boar to Poseidon (11.121–131). The rest of that meeting is on who Odysseus met in the underworld.

How far the grudge reached

The poem opens with the anger already old. All the gods pity Odysseus except Poseidon (1.19–21), and Zeus explains: the sea god will not kill him, but keeps driving him from home for blinding Polyphemus, his son by the sea nymph Thoosa (1.68–75). The gods free Odysseus from Calypso only while Poseidon is away, feasting among the Ethiopians.

On his way back the god sights the raft on its eighteenth day at sea and wrecks it with every wind at once (5.278–296). Odysseus swims ashore among the Phaeacians, and they pay for helping him. Poseidon tells Zeus he had meant Odysseus to come home only after much suffering, never to be spared it, and now strangers have carried him home loaded with gifts (13.125–138). With Zeus’s leave, he turns their ship to stone in sight of its own harbor (13.159–164).

Homer never says the god is right. A son was maimed and a father took revenge, and the man who did it had handed over his own name.