Etymology and distribution of 大県.

Oogata 【大県】^{レベル2
About 30}  The Japanese surnames etymology dictionary.

Okayama-ken Kurashiki-shi . A variant of 小川 . Okayama-ken Okayama-shi Kita Ward Marunouchi was in the Edo period in the Clan Okayama of the Clan office. 小川 Ogawa reference.