Etymology and distribution of 小井口.

Koiguchi 【小井口】^{レベル3
About 70}  The Japanese surnames etymology dictionary.

Oosaka-fu , Hyougo-ken , Toukyou-to .

① Korea type . A variant of 坡平 . There is a record of naturalization on Toukyou-to Oota-ku on December 15, 1960. There is also "Parow". The real name is Yoon. 尹 In reference. 坡平 Habira reference.

② Topography . From the slope. There are cases where Hira means "sloping ground". In the southwest part of Oosaka-fu (formerly Izumi-kuni), there is a record of the place name of Saka Hiraso in 1306 (Yoshimoto 4). The place name is the same as Sakamoto-so in estimation. It is distributed in Yamaguchi-ken Iwakuni-shi . Yamaguchi-ken Iwakuni-shi Nishiki cho Hirose Sakahei is a place name unknown in the record era.