Naming of moons underworld, and Nix (a respelling of Nyx), mother of Charon, is the goddess of darkness and the night. Kerberos is a giant three-headed dog who guards the entrance to the underworld. The fifth moon is named for the river Styx that forms the boundary between the worlds of the living and the dead. The name of Eris's moon Dysnomia was suggested by its discoverer Michael E. Brown, who also suggested the name of the dwarf planet. The name has two meanings: in mythology Dysnomia (lawlessness) is the daughter of Eris (chaos). However, the name is also an intentional reference to
The Dog It Was That Died be seen as the mad dog of the poem. Stoppard may have borrowed the idea to use this quotation from British novelist W. Somerset Maugham's 1925 "The Painted Veil", in which the protagonist's husband, bitter at her infidelity, brought her to cholera-stricken China in hopes that she would take ill and die. When he catches cholera instead, he dies with the quotation "The dog it was that died" on his lips. The words also occur in a speech by Wormold, the lead character in Graham Greene's 1958 novel "Our Man in Havana" – also an entertaining tale of Cold War