Because two kinds of characters to express the pronunciation of "ko" found in the ancient special Kana usage are not distinguished while エ of the row of ア in the gojuonzu (a "fifty-sound" syllabary chart) and エ of the row of ヤ are distinguished, Ametsuchi no Uta is thought to have been established in the beginning of Heian period (around A.D. 900).
上代特殊仮名遣のコの甲乙の区別は存在しないが、ア行のエとヤ行のエを区別している点から、平安初期（900年前後）の成立と見られる。