90482 Orcus objects with a similar size and orbit to that of Pluto are named after underworld deities. Accordingly, the discoverers suggested naming the object after "Orcus", the Etruscan god of the underworld and punisher of broken oaths. He was portrayed in paintings in Etruscan tombs as a hairy, bearded giant. The name was also a private reference to the homonymous Orcas Island, where Brown's wife Diane had lived as a child and that they visit frequently. On March 30, 2005, Orcus's companion, Vanth, was named after a winged female demon of the Etruscan underworld. She could be present at the moment
90482 Orcus with the normal object naming procedures. Vanth was found at 0.25 arcsec from Orcus with magnitude difference of . Estimates made in 2009 by Mike Brown show that the apparent magnitude of Vanth is which is magnitudes fainter than Orcus. Assuming equal albedos this would mean a diameter of 280 km, or 2.9 times smaller than the primary. However, the dissimilar colors of Orcus (neutral) and Vanth (red) suggest that Vanth could have an albedo a factor of two lower than Orcus. Should Vanth have an albedo of only 0.12, Vanth could be as large as 380 km with Orcus