plate
堞 centers on a flat, thin structural piece: a plate. The meaning is narrow and concrete, referring to a plate-like object, likely in a construction or architectural context.
堞 combines 土 (earth, soil) with 枼, which likely contributes the sound. The exact historical development is uncertain, but the character likely originally referred to a plate-like earthen structure or a flat piece used in construction.
The left side 土 suggests earth or clay, and the right side 枼 looks like a flat, segmented object. Picture a clay plate being shaped from the earth: 堞 is a plate.
For チョウ, imagine a plate being used as a gong, making a resonant 'choh' sound: Chou -> チョウ, and the plate rings out.