köken: Sino-Korean word from 冥王星, from 冥 (“dark, gloomy; chthonic”) + 王 (“king”) + 星 (“star”), from an orthographic borrowing from Japanese 冥王星 (Meiōsei).
alternative letter-case form of Diêm Vương tinh (“Pluto”) (Kuiper belt object - a dwarf planet)
köken: Sino-Vietnamese word from 閻王星, composed of 閻王 (“King Yama”) and 星 (“star”), from Chinese 閻王星 /阎王星 (Yánwángxīng), calque of Japanese 冥王星 (Meiōsei, Minh Vương tinh), coined by replacing the rather obscure 冥王 (Meiō, Minh Vương, “Netherking”, i.e. Pluto) with the better known 閻王 /阎王 (Diêm Vương).
Etimoloji
From 冥王 (Meiō, “King of the Underworld”) + 星 (-sei, “planet”), coined by Hōei Nojiri in 1930 as a reference to Pluto, the Greco-Roman god of the underworld.