Charon
Pluto's great moon
Today this word meansPluto's largest moon — big enough that the two orbit each other.
Discovered by Christy in 1978 and given the name of the underworld ferryman — fitting, for a body circling Pluto.
Its diameter is more than half Pluto's, so their common center of mass lies outside Pluto. It is effectively a double body.
Worth noting
The discoverer actually took the name from his wife Charlene and matched it to the myth afterward — which is why he pronounced it "SHAR-on."