Gyūdon (牛丼, "beef bowl"), also known as gyūmeshi (牛飯 or 牛めし, "beef [and] rice"), is a Japanese dish consisting of a bowl of rice topped with beef and onion, simmered in a mildly sweet sauce flavored with dashi (fish and seaweed stock), soy sauce and mirin (sweet rice wine). (Wikipedia).
[It] is considered to be derived from gyūnabe (牛鍋), a beef hot pot originating in the Kantō region of eastern Japan, first served in Yokohama in 1862. (Wikipedia). (Just One Cookbook).