Etymology and distribution of 内川口.

Uchikawaguchi 【内川口】^{レベル2
About 10}  The Japanese surnames etymology dictionary.

Kagoshima-ken Ooshima-gun Tokunoshima-chou . Terrain . "Oka" was added to Etsu which is the surname of Amagi archipelago of Kagoshima-ken . Estimated at the time of returning to Japan in 1953. 悦 Etsu reference.