What is "axylus"

Axylus is mentioned in Book VI of Homer's Iliad.

Diomedes, expert in war cries, killed Axylus, son of Teuthranus, a rich man, from well-built Arisbe. People really loved him, for he lived beside a road, welcomed all passers-by into his home. But not one of those men he'd entertained now stood in front of him, protecting him from wretched death. Diomedes took the lives of two men--Axylus, and his attendant Calesius, his charioteer. So both men went down into the underworld.