Hirakawa 【平川】6 The Japanese surnames etymology dictionary.
① There is a 御牧 family name. Kagawa-ken Takamatsu-shi Tamamocho is a clan official in the Edo period, Kumamoto-ken Kumamoto-shi Chuo-ku Honmaru was in the Edo period in the Kumamoto samurai of the Clan office.
② Topography . Ishikawa-ken Suzu-shi Meiji New surname by monk of Honjo Temple of Jodo Shin Buddhism in Misakiicho Uji. It is said that the vicinity of the same place was the horses' production area and that there was a designation of "Maki (Mimaki)".