Do ふえる and へる have a common etymology?


I was reviewing my Anki cards and it said that 減少 and 増加 are antonyms. Now,
for extra practice, I try to give at least one kunyomi reading to each kanji.
Then it occured to me that ふえる and へる sounded similar. This question may sound
crazy and naive, but could they be etymologically related, considering that
some words spelled with え now used to be spelled with へ?




In Japanese, phonetic equivalence is generally a very poor predictor of common
etymology. Japanese is well known as having a preponderance of homophones,
mostly due to the accretion of possible readings for each kanji which has
developed over the centuries. But even among wago (和語), verbs ending in 'eru'
are extremely common. Still, it is always worth researching individual cases.

A search of the words on Daijirin doesn't reveal evidence of a common
etymology, at least from the definitions
[here](https://kotobank.jp/word/%E5%A2%97%E3%81%88%E3%82%8B%E3%83%BB%E6%AE%96%E3%81%88%E3%82%8B-371400)
and [here](https://kotobank.jp/word/%E6%B8%9B%E3%82%8B-625738). I also checked
Kojien (広辞苑第六版) - it lists 減る as appearing in the '[Genpei
Sesuiki](https://en.wikipedia.org/wiki/Genpei_J%C5%8Dsuiki)', an extended
version of the [Heike
Monogatari](https://en.wikipedia.org/wiki/The_Tale_of_the_Heike)
(approximately 12th century). According to Daijirin, 減る also appears in the
[Koyo Gunkan](https://en.wikipedia.org/wiki/K%C5%8Dy%C5%8D_Gunkan) (17th
century), so presumably, the word was in regular use during the interim
period. I couldn't find any contemporaneous examples of 増える, checking in the
same Kojien edition and Shinmeikai (新明解国語辞典 第五版). That doesn't mean it wasn't
in regular use, of course. But without solid examples of usage that provide
context for the words, I can't find any evidence to support your hypothesis of
a common etymology.

Nonetheless, it's an interesting hypothesis in light of the phonetic changes
you mention. However, I think we need more details on how those specific words
might have undergone change before we draw any solid conclusions about their
derivations.




In Japanese, phonetic equivalence is generally a very poor predictor of common
etymology. Japanese is well known as having a preponderance of homophones,
mostly due to the accretion of possible readings for each kanji which has
developed over the centuries. But even among wago (和語), verbs ending in 'eru'
are extremely common. Still, it is always worth researching individual cases.

A search of the words on Daijirin doesn't reveal evidence of a common
etymology, at least from the definitions
[here](https://kotobank.jp/word/%E5%A2%97%E3%81%88%E3%82%8B%E3%83%BB%E6%AE%96%E3%81%88%E3%82%8B-371400)
and [here](https://kotobank.jp/word/%E6%B8%9B%E3%82%8B-625738). I also checked
Kojien (広辞苑第六版) - it lists 減る as appearing in the '[Genpei
Sesuiki](https://en.wikipedia.org/wiki/Genpei_J%C5%8Dsuiki)', an extended
version of the [Heike
Monogatari](https://en.wikipedia.org/wiki/The_Tale_of_the_Heike)
(approximately 12th century). According to Daijirin, 減る also appears in the
[Koyo Gunkan](https://en.wikipedia.org/wiki/K%C5%8Dy%C5%8D_Gunkan) (17th
century), so presumably, the word was in regular use during the interim
period. I couldn't find any contemporaneous examples of 増える, checking in the
same Kojien edition and Shinmeikai (新明解国語辞典 第五版). That doesn't mean it wasn't
in regular use, of course. But without solid examples of usage that provide
context for the words, I can't find any evidence to support your hypothesis of
a common etymology.

Nonetheless, it's an interesting hypothesis in light of the phonetic changes
you mention. However, I think we need more details on how those specific words
might have undergone change before we draw any solid conclusions about their
derivations.

