Shakespeare). All the retrograde irregular moons are named after characters from one play, The Tempest; the only prograde irregular moon, Margaret, is named from Much Ado About Nothing. Neptune The one known moon (at the time) of Neptune was not named for many decades. Although the name Triton was suggested in 1880 by Camille Flammarion, it did not come into general use until the mid 20th-century, and for many years was considered "unofficial". In the astronomical literature it was simply referred to as "the satellite of Neptune". Later, the second known moon, Nereid, was named by its discoverer in 1949, Gerard P. Kuiper, soon after its discovery. Current IAU practice for newly discovered Neptunian moons is to accord with these first two choices by naming them after Greek sea deities. For the "normal" irregular satellites, the general convention is to use names ending in "a" for prograde satellites, names ending in "e" for retrograde satellites, and names ending in "o" for exceptionally inclined satellites, exactly like the convention for the moons of Jupiter. Pluto The name of Pluto's moon Charon was suggested by James W. Christy, its discoverer, soon after its discovery. The other four moons are named Hydra, Nix, Kerberos, and Styx. Charon, Hydra, Nix, and Kerberos are all characters in Greek mythology, with ties to Hades (the Greek equivalent of Pluto). Charon ferries the dead across the River Acheron, Hydra guards the waters of the 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. Eris 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 actor Lucy Lawless who plays the character Xena. The background for this is that during the long period when Eris had no formal name, the name 'Xena' – originally Brown's nickname for his discovery – spread and became popular. When the name 'Eris' was chosen, Brown suggested Dysnomia (which until then had been referred to as Gabrielle) as a reference to