thin kimono
衫 centers on a specific type of lightweight garment: a thin kimono. The meaning is narrow and concrete, referring to a particular clothing item.
衫 combines the clothing radical 衤 with 彡, which likely contributes a phonetic element. The character is used for a thin garment, but the exact historical development of the 彡 component here is uncertain.
The left side 衤 shows a garment, and the right side 彡 looks like delicate, flowing lines. Picture a thin kimono made of such light fabric that its folds create soft, wispy shapes.
For サン, imagine the thin kimono being worn under the sun: sun -> サン, and the light fabric feels cool in the sunlight.
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