いお【魚】 : io | define meaning

Cognate to the regional Japanese word うお uo or いお io "fish" (considered outdated or obsolete in the standard language); Ehime and Amakusa (Kumamoto) いを iwo; Ehime, Nagasaki, Kumamoto and Kagoshima いお io; Kagoshima いよ iyo; Kikai いゆ iyu, いう iu and ゆ yu; Amami (Kamikatetsu) ゆ yu; Amami (Yuwan) and Okinawan (Nakijin) っゆ qyu; Amami (Yamatohama, Asama, Shodon), Yoron and Okinawan (Yonamine) っゆー qyuu; Okinawan (Shuri) いう iu and いゆ iyu; Miyako (Irabu) ïzu; Miyako (Hirara) (z)ïzu / ɿzu / zzu; Yaeyama (Hateruma) ゆー yuu; Yaeyama (Ishigaki) いづ idzu; and Yonaguni いゆ iyu. Written as うを uwo and いを iwo in Classical Japanese.

Attested for Japanese in the 和名抄 Wamyōshō (938 CE) under the spelling 宇乎 uwo, with a note mentioning the vulgar pronunciation 伊遠 iwo. Attested for Ryukyuan under the spelling eéo (io) "fish" in the 1818 Vocabulary of the language spoken at the Great Loo-Choo island in the Japan Sea, by Herbert John Clifford.

Variously reconstructed for Proto-Ryukyuan as *iyu, *iyo or *io. Variously reconstructed for Proto-Japonic as *uCo, *iCo, *uwo, *iwo, *(d)íwó, or *(y)iwə.