Do 臭い{くさい} and [腐る]{くさる} have similar roots? They obviously sound very similar; the only difference in pronunciation is the final mora, but maybe that's only because of the part of speech. The meanings are related as well. When things rot, they tend to smell bad. Of course, 臭い isn't restricted to just bad food, but meanings tend to change/broaden over time.

So I'm wondering, were these once pretty much the same word, separated once they were given kanji? Or have they always been thought about separately, and the sound/meaning is just coincidence?

1 Answer 1


語源由来辞典 lists theories that they might be connected for the very same reason you mentioned, among others.


The way I understand it, it is generally believed that 腐る, along with くそ, stems from 腐る, but that is not proven (and there are other conflicting theories, such as 腐る stemming from 糞荒【くさあるる】, whose reading I can't quite explain).

Apart from that, I've been able to retrieve two related citations from the 岩波古語辞典, from two different sources. The first one is for 腐り, from a Yahoo! question.


The second one is for 臭し (classical form of 臭い), which can be found here.

<クサリ(腐)・クソ(糞)と同根> はげしい、いやなにおいがする。悪臭を放っている。

As you can see, both entries cross-reference each other.

So, it seems like the 腐る・臭い connection is definitely the most agreed upon theory, although there does not seem to be a definite proof. There definitely seems to be some kind of connection between (at least two of) くそ, くさい and くさる, though, although we can't know for sure how exactly it's laid out.

  • I'm curious, where did you find reference to 糞荒 as くさあるる? My copy of Shogakukan's Kokugo Dai Jiten lists the etymology of 糞{くそ} as cognate with 臭{くさ}い, itself listed as cognate with 腐{くさ}る. In terms of readings, the あるる portion would be the classical attributive conjugation of root verb 荒{あ}る, realized in modern Japanese as 荒{あ}れる. Jun 21, 2015 at 22:37
  • The source can be found at the top of my post: gogen-allguide.com/ku/kusaru.html I have to admit that my knowledge on classical Japanese is limited, so I cannot provide you with a qualified explanation of this.
    – looki
    Jun 22, 2015 at 4:23

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