88721
Why is the volitional form of する - しよう, considering the pre-spelling reform
but post-む form was せう, which according to sound changes and modern kana
orthography should become しょう? Especially considering we have でしょう and ましょう,
which come from the expected でせう and ませう, where the せう becomes しょう - but how
come せう as in する irregularly becomes しよう?

This would also apply to 二段活用 verbs - why do [食]{た}ぶ and [閉]{と}づ become
[食]{た}べよう and [閉]{と}じよう instead of [食]{た}びょう and [閉]{と}じゅう as would be
expected from 食べう and [閉]{と}ぢう?

Additionally - where does [来]{こ}よう come from? A jump from [来]{こ}う to [来]{こ}よう
seems quite drastic.
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2021-08-01T06:15:43.953
88700
2021-08-02T14:39:09.173
39722
question
verbs pronunciation kana volitional-form obsolete-kana
Why is the volitional form of する - しよう, considering the classical post-む pre-spelling reform form was せう which should net *しょう?
According to Frellesvig, B. (2010). A history of the Japanese language.
Cambridge: Cambridge University Press, in Late Middle Japanese the verbs did
have the volitional forms that is implied by the addition of -う to the 未然形
form; that is, せう(= _syoo_ ), 開けう(= _akyoo_ ), 寝【ね】う(= _nyoo_ ), 起きう(= _okyuu_
), 見【み】う(= _myuu_ ) in parallel with 書かう(= _kakɔɔ_ ) and 持たう(= _motɔɔ_ ).

However, in Modern Japanese, the volitional form have changed; this is best
explained as an analogical change.

  * As /ɔɔ/ (=あう) and /oo/ (=おう) merged, the suffix was reanalyzed as _-(y)oo_ , making the volitional form of 上一段活用 [見【み】う(= _myuu_ )] and 上二段活用 [起きう(= _okyuu_ )] outliers to the paradigm
  * As the former 二段活用 became levelled to 一段活用, the conjugation paradigm of 開け- was no longer alternating between _ake-_ and _aku-_ ; instead it was levelled to a single form, _ake-_. The volitional form _akyoo_ is thus an outlier to the paradigm

Hence we have 開けよう, 寝よう, 起きよう, 見よう as the new paradigm of volitional forms,
resolving both of these outliers while also making -う/-よう parallel with
-せる/-させる, -れる/-られる in that they care whether the preceding verb is 四段 (or, 五段
after the spelling reform) or not.

Languages tend to make changes unpredictable from sound laws, and in many
cases (especially in verbal paradigms) such changes are fuelled by analogical
levelling. For instance, Old French had **tons** of vowel alternations (caused
by sound laws from Latin to Old French) such as leve / laver, aime / amer,
trueve / truver, many of which have lost the alternations in the contemporary
language (lave / laver, aime / aimer, trouve / trouver).

<https://en.wikipedia.org/wiki/Old_French#Verb_alternations>
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2021-08-02T14:39:09.173
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answer