I noticed there are many 形容詞{けいようし} (i-adjectives) that end in 〜ない, where the な is not part of the kanji, and doesn't seem to have the meaning 無い.
Examples:
- 危{あぶ}ない means "dangerous", while 危 means "danger"
- 少{すく}ない means "few"/"scarce", while 少 means "few"/"little"
- 切{せつ}ない means "heartrending"/"trying", while 切 means "earnest"/"ardent"
(For contrast, examples where it's clearly 無い: 心ない, 情けない, 力ない.)
I wonder where exactly this ない is coming from. It is not a classical Japanese ending to my knowledge (like 〜しい).
I speculate that it could be an alternative shortening of the classical Japanese copula 〜なり, but this is odd to me because I suspect the usual shortening of 〜な would be used if this were the case (as we see in 形容動詞{けいようどうし} (na-adjectives)).
Does anyone know the etymology of these words and/or the meaning of this 〜ない?