Hades three-headed guard dog Cerberus. The Etruscan god Aita and the Roman gods Dis Pater and Orcus were eventually taken as equivalent to Hades and merged into Pluto, a Latinization of Plouton (", Ploútōn"), itself a euphemistic title often given to Hades. The origin of Hades' name is uncertain, but has generally been seen as meaning "the unseen one" since antiquity. An extensive section of Plato's dialogue "Cratylus" is devoted to the etymology of the god's name, in which Socrates is arguing for a folk etymology not from "unseen" but from "his knowledge ("eidenai") of all noble things". Modern linguists have
90482 Orcus relatively large satellite (Vanth, see below) may change them considerably. The absolute magnitude of Vanth is estimated at 4.88, which means that it is about 11 times fainter than Orcus itself. If the albedos of both bodies are the same at 0.23 then the size of Orcus is about , and the size of Vanth is about . The ALMA submillimeter measurements taken in 2016 showed that Vanth has a relatively large size of with albedo of about 8% while Orcus' has a slightly smaller size of 910 km. Using a stellar occultation by Vanth in 2017, Vanth's diameter has