The Japanese surnames etymology dictionary.
① Topography . From the big under the land. Hiroshima-ken Hiroshima-shi In the Minami-ku Nagashima-cho told me that Meiji New surname . Hiroshima-ken Hiroshima-shi Naka-ku Kamamachi was in the Edo period in the Hiroshima samurai of the Clan office. Iwate - ken Kunohe - gun Hirono - chou Tell the deer in the lake in the Town City that there was a house at the bottom of the same place. Iwate - ken Kunohe - gun Hirono - chou There is a belief that Mr. Sakashita lived in below in Otsuko . 坂下 reference.
③ Convention . Synthesis of Okawara and Shimokawara. In Iwate-ken Miyako-shi Kariya, when saying Meiji New Last Name, we say that we combined "Okawara" 's "Great" and Shimokawara's "Down". 大川原 reference. 下川原 reference.