laugh, smile
唹 centers on expressing amusement or joy through sound: laughing or smiling.
唹 combines 口 (mouth) with 於, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound related to vocal expression.
A mouth 口 beside 於: picture a mouth opening wide in a laugh, with the right side suggesting the sound of laughter.
For オ, imagine a surprised laugh: 'Oh!' — the mouth 口 opens and the sound オ comes out.
—