underwear
襯 centers on clothing worn next to the skin: underwear or an undergarment.
襯 combines 衤 (clothing) with 親, which likely contributes the sound シン. The character is used for undergarments, but the exact historical development is uncertain.
The clothing radical 衤 beside 親 suggests a garment that is close or intimate, like underwear worn directly against the body.
For シン, imagine thin underwear made of sheer fabric: thin -> シン, and the clothing radical 衤 reinforces the garment idea.
underwear; shirt (worn as an undergarment)