The Origins of the Vowels e₁ and o₁ of Old Japanese

Abstract

The vowels el and oi are developed by the widening of the mouth aperture as e₁<i₁ and o₁<u. Vowel syllables, however, have developed as 'i₁<ye₁<ye and 'u<wo₁<wo. These sound changes took place not so long before the eighth century.
Since the duration when Old Japanese was available is rather short, older lexical evidences do not always show older forms but may be forerunners of innovation. The widening is proved by pairs of words which have suffered other sound changes. In the case of e₁, fuki₁ (blowing) and fuye (flute) can be linked with intermediate *fui₁, which is the starting-point of the widening as well as the goal of “i-reduction.” In the case of o₁ simo₁ (below) and the first morpheme of siduye (low branch) have the common ancestor *simu, which explains both the widened vowel and the disappearance of mu with the vocalization of the following consonant. The rules of hiatus avoidance and alliterative epithets also support the inference.
A popular theory of the origins of e₁<i₁+a and o₁<u+a cannot hold good. The only word which is said to be evidenced, ari (be), is suspicious with the very initial a, because it violates the hiatus rule. We had better think that an allomorph ri was used in those compounds and the form ari is a variant of ri with a parasitical appendant vowel.