Pluto.

Internationalism, based on Latin Plūtō (“Pluto, god of the underworld”), from Ancient Greek Πλούτων (Ploútōn, “Plouton, god of the underworld”), formed from πλοῦτος (ploûtos, “wealth, riches”) + -ων (-ōn, “possessive suffix”). The divine name therefore meant approximately “the rich one”, an epithet of the ruler of the underworld, associated not only with the dead but also with the riches and fertility contained within the earth. The common noun πλοῦτος (ploûtos) has traditionally been connected with the root of πλέω (pléō, “to float, sail”), perhaps through an older semantic development “to flow” → “to abound”, though its deeper etymology is uncertain. The astronomical sense is transferred from the name of the deity. Clyde Tombaugh discovered the object in 1930 at the Lowell Observatory. The name Pluto was suggested by eleven-year-old Venetia Burney, and was appropriate for a distant, dark world named after the god of the underworld; its first two letters, P and L, also commemorate Percival Lowell, whose work had initiated the search for a planet beyond Neptune. Pluto was regarded as the ninth planet until 2006, when the International Astronomical Union reclassified it as a dwarf planet. Parallel international forms include Danish Pluto, Swedish Pluto, German Pluto, Dutch Pluto, Finnish Pluto, Icelandic Plútó and English Pluto.