Origin of the kanji for 叶う

Question

One thing that has always confused me is how the word 叶【かな】う took on the meaning of for a (wish) to come true. I find this perplexing because in Chinese, the word has never had this meaning. 叶's ancient meaning was:

叶：古文協字。 (Meaning the same as 協)

More recently, 叶 has become the character in simplified Chinese meaning 葉 because it has historically been mistakenly used as a replacement due to being similarly sounding.

However, neither of these meanings are at all close to a wish coming true.

Why/when/how did the kanji 叶 become associated with this meaning?

Answer 1

"Come true" isn't the literal translation of 叶{かな}う. The word かなう means "to fit; match; accord", in this sense in accord with 叶's meaning in Classical Chinese. So we are practically saying 願いが叶う "my wish matches it" as if a fixed phrase corresponds to "my wish comes true".

かなう once had tons of kanji transcriptions (see below), but most of them were culled out and only 適, 叶 and 敵 are left standardized. 叶, despite definitions in several dictionaries, is not only for "come true"; it can also be used where you can use 適, e.g. 「法に叶い、理に叶い、情に叶う」, which reflect more of its original meaning. That said, it's not vice versa; 適 can't be used where it means "come true". The actual process how 叶 becomes the only allowed kanji for "come true" is yet to be confirmed, but I guess it was chosen because it was a fallen-out-of-use character that was convenient for recycling. A similar example is 咲, which originally was an obsolete variant of 笑, but is only used for a different meaning today.

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(from 類聚名義抄仮名索引)