Kokusu 【古楠】2 The Japanese surnames etymology dictionary.
Tokushima-ken , Hokkaidou , Oosaka-fu . Terrain . Ken-Tokushima Yoshinogawa-Shi in the Kamojima of Tokushima-Ken Yoshinogawa-Shi and yesterday the samurai of Goto last name was in Kawajima there was Kawashima castle in Kawashima tell that it has added a "field". Estimated in the Azuchi Momoyama period. 後藤 reference.