In the book motorcycle and sweetgrass why does John have multiple names?

At the beginning of the book John is presented as a very mysterious figure who arrives in town on a motorcycle. Everyone in the book seems to be intrigued and curious about him. He has the ability to change his eye colors and his age, which gives him the facility to change names.

He has these 'mystical' powers due to his real identity being the "Nanabush", a historical creature from an Ojibwe legend told by the character Lilian, a woman who at the moment of dying refers to John as being "magic" on his first appearance.