What is the origin of けれど, ければ, けど, etc?


In Classical Japanese (correct me if I'm wrong; all my CJ was from Wikipedia
and linguistic papers), the 已然形 could attach a lot of things: ど, ば, ども, etc.
So I would be able to say 会へども話せず rather than 会うけれど話せない?

Anyways, where does the `ker-` part come from in all these supplanted forms of
the 已然形? Is there once some helping 四段 verb ける? If so, what would it mean?




They are conjugational endings from (sh)i-Adjectives:

We can derive verbs from adjectives by adding あり:

> 赤し -> 赤く＋あり -> 赤かり

And conjugate them further:

  * 赤かれ＋ば
  * 赤けれ＋ど(も)
  * 赤からず (negation)
  * ...

This conjugational suffix got reanalyzed as a word on its own, yielding けれども,
which was shortened to けれど, けども, and けど.

Even けれ by itself was used in the meaning of けれども by the same process.

日本国語大辞典

> けれ：この助詞が現れたのは、文語の形容詞の「数こそ多けれ、すぐれたるは少し」の_
> _「多けれ」のような用法から、「けれ」そのものに「が」「けれども」の意がある_ _と考えたためであろうといわれる。〔徳川時代言語の研究=湯沢幸吉郎〕




They are conjugational endings from (sh)i-Adjectives:

We can derive verbs from adjectives by adding あり:

> 赤し -> 赤く＋あり -> 赤かり

And conjugate them further:

  * 赤かれ＋ば
  * 赤けれ＋ど(も)
  * 赤からず (negation)
  * ...

This conjugational suffix got reanalyzed as a word on its own, yielding けれども,
which was shortened to けれど, けども, and けど.

Even けれ by itself was used in the meaning of けれども by the same process.

日本国語大辞典

> けれ：この助詞が現れたのは、文語の形容詞の「数こそ多けれ、すぐれたるは少し」の_
> _「多けれ」のような用法から、「けれ」そのものに「が」「けれども」の意がある_ _と考えたためであろうといわれる。〔徳川時代言語の研究=湯沢幸吉郎〕

