Etymology and distribution of 率川.

Isagawa 【率川】^{レベル2
About 20}  The Japanese surnames etymology dictionary.

Aichi-ken Komaki-shi , Toukyou-to . Niigata-ken , Ugimi at Nagano-ken . Originated from Niigata-ken Jouetsu-shi near Sanwa-ku (formerly known as the fifty-daimyo town). A place name with a record since the Nara period. Niigata - ken Odjiya - shi Iwasawa tells Mr. Fujiwara named Niigata - ken Jouetsu - shi in the vicinity of Takada after the turbulence in 939 (the second year of Tiankei). 藤原 Fujiwara reference.