Omisou

…It is also written as “masu-sui” because a large amount of water is added, and dried radish leaves were often added to the rice to bulk it up. In the past, it was called “misou-zu” and in women’s language, it was called “omisou” or “ojiya.” “Miso-zu” is written as “misou-sui,” “miso-sui,” or “soy-sui,” and is said to have been named after the miso used for flavoring. …

*Some of the terminology explanations that mention "omisou" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…多量の水を加えるところから増水とも書き，ダイコンの干葉（ひば）などを米の増量材として加えることも多かった。古く〈みそうず〉といい，女房詞（にようぼうことば）では〈おみそう〉〈おじや〉といった。〈みそうず〉は未曾水，味噌水，醬水などと書かれ，みそで味をつけたための名とされる。…

※「おみそう」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報