Saida 【斉田】5 The Japanese surnames etymology dictionary.
① variant of 笹川 . Toyama-ken Toyama-shi Honmaru was a Toyama clan of the clan government, Hyougo-ken Tanba-shi Kashiwabara-cho Kashiwabara was in the Edo period in the Kashiwabara clan of the clan office. Kashiwabara clan says that Fukushima-ken Koriyama shi Azusa - cho Sasagawa comes out and also marked "Sasagawa" in the Edo period. 笹川 reference.
② Yamaguchi-ken Hagi-shi Originated from Kasasao (Sasao) and Shimosasao in the lower of the upstream. Kawakami is a place name with a record since the Edo period. From "Sasa" of Sasao, and "River" at Kawakami. Last name was also written as "Sasagawa". Yamaguchi-ken Hagi-shi Horiuchi was in the Edo period in the Choshu clan of the clan office. Tradition of the same samurai. 笹川 reference.