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They sound alike. Are they cognate historically?

Morphologically, is よ in both cases a particle or part of the morpheme in
-ましょう?
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2012-12-27T21:26:24.437
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2012-12-28T15:24:24.877
2012-12-27T22:44:48.337
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1841
question
particles verbs etymology suffixes
Relation between -ますよ and -ましょう
The short answer to your initial question is no. The historical/etymological
spelling of 〜ましょう was 〜ませう, which is the expected form of the volitional,
since the irrealis (未然形) stem of 〜ます is 〜ませ. Regular sound change explains the
rest: せう becomes しょう.

The same story applies to the consonant-stem (五段活用) verbs: the old spelling
for 行こう was 行かう (as seen
[here](http://commons.wikimedia.org/wiki/File%3aAffiche_%C3%A9migration_JP_au_BR-d%C3%A9b._XXe_s..jpg))
etc. However, something strange happened to the vowel-stem (一段活用) verbs;
instead of 見む → 見う → **みゅう or せむ → せう → **しょう, these were replaced by the
forms with 〜よう we know today.
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2012-12-28T15:24:24.877
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2012-12-28T15:24:24.877
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answer