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The letter was originally the combination of ⟨ㅏ⟩ and ⟨ㅣ⟩ as verified from the description of the chapter "An Explanation of the Medials (中聲解)" of the Hunminjeongeum Haerye. In the 15th century, the letter was originally pronounced as the diphthong /aj/, however, it was not included with the 11 medial letters, along with ㅕ, ㅛ, ㅠ, which started with the letter ⟨ㅣ⟩.
From the 18th and 19th century, the change of pronunciations of the word is attested by confused notations with ㅔ.
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