When Odysseus was hunting on Mount Parnassus as a boy, he was injured by a wild boar. He did kill it, but it got a piece of him as well. It was a cut that ran just up from his knee. That wound ended up scarring his leg, and only a few people know if it. His nurse Eurycleia would be one who knew that scar. Men wore their long tunics down just past their knees, so very few people would be able to see it. She saw it and knew right away who he was. Although he was disguised as an old beggar, she knew that Odysseus was finally home to reclaim what was rightfully his.