いる/える Godan Verb Rules?


For words like 帰ります is there a specific reason they're Godan instead of
Ichidan in any case? Things like a change from an historical pronunciation of
the word, grammar relating to the radicals of the character or is it literally
random with each of these decisions genuinely being made arbitrarily? For 帰ります
just for the sake of example, what was the original reason it's Godan and how
many other いる/える Godan verbs have similar stories?




I think you are approaching this the wrong way. You seem to assume that all
verbs that end in _-eru_ or _-iru_ **should** be _ichidan_. But there's no
reason why that should be true. In linguistics there are no "shoulds". It's
just the way that the verbs are.

Let's try looking at this from another angle. Consider the inflections for the
_ichidan_ verb _kaeru_ = "to change" (変える). As you know, inflections are the
part of the word that changes; in languages like English and Japanese, that
happens at the end of the word. I will separate the part that doesn't change
(the "base", "radical" or "stem") with an hyphen:

  * **_kae** -nai_
  * **_kae** -masu_
  * **_kae** -ru_
  * **_kae** -re-ba_
  * **_kae** -yo_

Now compare the stem for the _godan_ verb _kaeru_ , "to return" (帰る):

  * **_kaer** -a-nai_
  * **_kaer** -i-masu_
  * **_kaer** -u_
  * **_kaer** -e-ba_
  * **_kaer** -ō_

Notice how, for the _ichidan_ verb 変える, the base or stem ends in a vowel,
_-e_. For the _godan_ verb 帰る, the stem (=the part that never changes) ends in
a consonant, _-r_. Because of this, linguists call the traditional _"ichidan"_
verbs **vowel-stem verbs** , and _"godan"_ verbs **consonant-stem verbs**.

So the fact that a verb has conclusive inflection ( _shūshikei_ 終止形,
dictionary form) ending in - _eru_ does not, by itself, tell us how it
inflects. We need to know whether the stem ends in a consonant or in a vowel.
"To return" has the stem _kaer-_ , and "to change" is _kae-_. It's just that
the conclusive form of vowel-stem verbs ( _ichidan_ verbs) adds _-ru_ , so
that, by coincidence, they end up sounding just like consonant-stem verbs
whose final consonant happens to _-r_.

* * *

Why are some verbs vowel-stem, and some verbs consonant-stem?

We don't know. The oldest records we have of Japanese are from the Nara
period, and at this stage the distinction was already present. In ancient
Japanese consonant verbs used four extra vowels, not five (so they were 四段
_yodan_ , four-grade, in Japanese terminology). And there were more kinds of
vowel-stem verbs, with some rules which made the vowel change, and more
irregular verbs, too. But the basic distinction between vowel-stem and
consonant-stem verbs, those like _kaer-u_ vs. _kae-ru_ , goes back as far as
we have evidence. For example, the verb _kaer-u_ "to return" has been
reconstructed as * _kapyer-_ (かへ甲る)¹, while "to change", _kae-ru_ , had the
ancient stem * _kape-_ (かへ乙-).²

Some linguists have proposed that all verbs were originally consonant-stem,
and vowel-stem verbs were derived from them. Others have argued for the
opposite. As far as I can tell, there's no definitive answer yet.

Frellesvig, in _A History of the Japanese Language_ (pp. 119–), notes two
phenomena that happen with ancient vowel-stem verbs. The first is that, in
many cases, the vowel-stem verb appears to be derived from an adjective, with
a change in vowel ( _aka-ki_ "red" → _ake-ru_ "redden, lighten"; _sabu-si_
"lonely" → _sabwi-ru_ "grow desolate"). In other cases, the vowel-stem verb
appears to be derived from a consonant-stem, changing the transitivity ( _tuk-
u_ "stick to" → _tuke-ru_ "attach something"). These alternations (both the
change in vowel quality, and the addition of an extra vowel) have been
theorized (by Ohno, Unger and others) to come from some prehistoric suffix *⁠
_-y_ , which formed diphthongs like _akay-_ , later changing into _ake-_ etc.

If this theory is correct, the reason why 変える _kae-ru_ is a vowel verb is
that, a very long time ago, it was formed with this hypothetical *⁠ _-y_
suffix, possibly from * _kapay-_ (compare 変わる _kawar-u_ < _kapar-u_ ). And the
reason why 帰る _kaer-u_ is not a vowel verb is that it never had such a
diphthong. But all of this is hypothetical; and even if it's correct, there
are still many modern vowel-stem verbs which would _not_ trace to these *⁠
_-y_ -verbs. The proposed *⁠ _-y_ formant would have created most of the
vowel-stem verbs, but not all³ (e.g. _mi-ru_ "to see" and _ki-ru_ "to put on"
appear to have been vowel-stems from the beginning).

* * *

Notes:

[1] There used to be two kinds of _e_ , called in Japanese linguistics the
"A-type" (甲) and the "B-type" (乙). I'm following Frellesvig in interpreting
A-type as _ye_ , and B as a plain _e_. Also the はへひほふ sounds used to be
_pa,pe,pi,po,pu_ ; in the middle of words they later became _wa,we,wi,wo,u_ ,
then finally _a,e,i,o,u_ (so _kapyeru_ > _kaweru_ > _kaeru_ ). The orthography
changed, accordingly, from かへる to かえる. These ancient pronunciations aren't
relevant for the discussion, so you can gloss over all that.

[2] One of the verb inflection rules was that, when two vowels met, you picked
the second. So _kapyer-_ plus the conclusive suffix _-u_ resulted in _kapyeru_
かへる; but _kape-_ + _-u_ > _kape+u_ > _kapu_ , かふ. The unchanged stem was
visible when you added a consonant-initial suffix, like _kape-te_ かへて, which
didn't change the original vowel. This rule accounts for the "bigrade" (ニ段)
verbs of traditional grammar.

[3] The verbs thought to be made with the *⁠ _-y_ formant are called
"thematic". For those familiar with traditional grammar, the thematic class
corresponds to lower bigrades 下ニ段, upper bigrades 上ニ段, and possibly the
s-irregular サ変.

