In a comment on the question Origin of あしからず, I wrote:

What about 必ず? It's from 仮 + ならず. Does that fit the 形容動詞 + ならず pattern?

I said this because 大辞泉's entry for 必ず says the following:


However, Dono responded by saying:

That is one suggested etymology, but there is no general consensus.

If there is no consensus, are there other explanations for the etymology of 必ず?

  • It's interesting that the fake etymology/memory device I give myself to remember this Kanji is "cross my heart and hope to die" but I wonder how much of that phrase goes back to a common etymology for the two i.e. does a similar saying exist in Chinese?
    – psosuna
    Sep 14, 2018 at 18:48

1 Answer 1


Firstly, 大辞泉 is known to have a number of issues. You should get a second opinion on much of what it says. I'm away from most of my resources for the weekend, but below are quotes from several more reliable dictionaries at hand.

大辞林: 〔補説〕 「仮(かり)ならず」からできた語か

時代別国語大辞典:上代編: ズは、おそらく否定の助動詞、カナラは活用語の未然形であろう。名義抄に「必(カナラジ)」とあるのも参考になる。そのカナラに関して、(イ)仮(かり)ナリの略、(ロ)兼ぬから派生した自動詞カナルを想定する、という説がある。(イ)は、仮でなく---ほんとうに、という意味変化の経路を(ロ)は、兼ねられてしまわずに---それだけが一すじに、というところからと考えるのであるが、いずれも決定的な根拠はない。

角川古語大辞典: 活用語の未然形に打消の「ず」の付いた形と考えられ、「必カナラジ(名義抄)」もこの推定を支える。「仮ならず」の転とする説、「彼ならず」の意とする説、「兼ぬ」から派生した動詞「かなる」を推定して、二道かけず一筋に、の意とする説などがある。

I am not strongly opposed, per se, to kari + narazu. A good argument may convince me. However, the evidence is lacking. Why does the medial -ri- disappear completely? Also, semantically, the relevance of 仮 to 必ず is questionable. Anyway, people have argued various etymologies over the years, but as above 「いずれも決定的な根拠はない」.

  • Somehow I'd gotten it into my head that this was か (question marker) + 成らず, i.e. "not in question" > "absolutely, certainly, no doubt". Shogakukan also gives this 「かり(仮)ならず」の変化 etymology, but I too am not convinced. May 28, 2014 at 6:33

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