Eurycleia recognizes Odysseus when she washes his feet, at Penelope's command, and sees a particular scar on his leg. Odysseus had gotten this scar, long ago before the Trojan War, during a boar hunting incident. Eurycleia knew about the hunting trip and the scar.

How does Eurycleia recognize Odysseus?

Eurycleia is the only person to recognize Odysseus by an old scar when he returns disguised as a beggar.

When did Eurycleia recognize Odysseus?

Only reluctantly does he allow Eurycleia to wash his feet. As she is putting them in a basin of water, she notices a scar on one of his feet. She immediately recognizes it as the scar that Odysseus received when he went boar hunting with his grandfather Autolycus.