Etymology and distribution of 小岩原.

Koiwahara 【小岩原】^{レベル2
About 30}  The Japanese surnames etymology dictionary.

Ooita-ken Ooita-shi . Ooita-ken Ooita-shi Originated from Omiwa no Owatari (Sashiwara) in Tanchawa. It was in the Edo era at the same place, Ooita-ken Usuki-shi . "Ohita-ken " was the notation of "Sugawara" to the vassal of Mr. Otomo who used it as the base of the Kamakura period and the Muromachi period. It is unknown whether the difference exists.