sound of laughter, sound of mice squeaking
咭 centers on high-pitched, repetitive vocal sounds: laughter or the squeaking of mice. Both meanings share the idea of a sharp, staccato noise produced by a mouth.
咭 combines 口 (mouth) with 吉, which likely contributes the sound. The character is used to represent sharp, repetitive mouth sounds such as laughter or squeaking.
A mouth 口 making a lucky 吉 sound: imagine someone laughing so hard they feel lucky, or a mouse squeaking happily over a piece of cheese.
For キツ, picture a mouse squeaking so sharply it sounds like a quick 'kits!' — the kits sound cues キツ while the mouse squeaks through the mouth 口.
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