ah, final particle
喲 is a rare kanji used as an interjection or sentence-final particle, expressing a sense of 'ah' or exclamation. Its meaning is essentially a vocal utterance rather than a concrete concept.
喲 combines the mouth radical 口 with 約, which likely contributes a phonetic element. The exact historical development is uncertain, but the structure suggests a character created for its sound value as a particle.
The mouth radical 口 on the left indicates speech or sound. The right side 約 (promise/approximately) can be thought of as a sound uttered to seal a promise: 'Ah, it's a deal!'
For ヤク, imagine a yak (ヤク) making a surprised 'ah!' sound with its mouth wide open. The yak's exclamation ties the reading to the meaning.
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