harness strap, window
紂 centers on a leather strap used to control a horse, specifically the crupper that passes under the tail. The rare window meaning is likely a separate, unrelated usage.
紂 combines 糸 (thread) with 寸, which may have contributed a phonetic element. The exact historical development is uncertain, but the character is associated with a leather strap, suggesting a connection to binding or tying.
The left side 糸 suggests thread or cord, and the right side 寸 looks like a hand measuring. Imagine a leather strap measured and threaded under a horse's tail to secure the harness.
For チュウ, picture a horse chewing on its harness strap: chew -> チュウ, and the strap keeps the harness in place.