His wife got "the planet" in the divorce and his bones were all that she left him.
Which is a dumb way to get a nickname. Furthered by the fact that for decades the explanation was that it was derived from the military nick name for a doctor - Sawbones.
Oh come on, nicknames are inherently dumb, that is the nature of things.
Nicknames are usually rediculous names given by friends, rarely are they thought out.