How does the loyal nurse Eurycleia recognize Odysseus?

In Homer's Odyssey, Eurycleia recognizes Odysseus by a scar on his leg, which he obtained while hunting a wild boar during his youth. This scar is a distinctive mark that Odysseus had kept since then. When Eurycleia is washing Odysseus' feet, she notices the scar and immediately recognizes him, despite the fact that he has been disguised as a beggar. This moment of recognition is a crucial turning point in the story as it confirms Odysseus' true identity and sets in motion the events leading to his eventual reunion with his wife, Penelope.