thin kimono, undergarment
褝 centers on a single-layer garment worn close to the body: a thin kimono or undergarment.
褝 combines 衤 (clothing) with 単, which likely contributes the sound and the idea of a single layer. The character is associated with a thin, unlined garment.
The clothing radical 衤 beside 単 (simple, single) suggests a simple single-layer garment: a thin kimono or undergarment.
For タン, imagine a thin tan-colored undergarment: tan -> タン, and the single layer shows a light tan.