pleat in a skirt
襵 centers on a fold or pleat in fabric, especially in a skirt. The other given meanings (folding, sewing, seam, rolling up) are actions related to creating or handling such pleats.
襵 combines 衤 (clothing) with 聶, which likely contributes the sound and relates to folding or layering. The exact historical development is uncertain, but the structure suggests a phono-semantic compound for a clothing-related fold.
The left side 衤 is clothing, and the right side 聶 looks like three ears stacked. Imagine folding a skirt into pleats that resemble rows of ears listening closely.
For ショウ, picture a fashion show where every pleat in the skirt is perfectly pressed: show -> ショウ, and the pleats are the star of the show.