rope
絚 centers on a rope, a strong cord made from twisted fibers.
絚 combines 糸 (thread) with 亙, which likely contributes the sound. The character is a phono-semantic compound for a rope or cord.
The left side 糸 is thread, and the right side 亙 looks like a spool or a stretched cord. Picture many threads twisted together into a strong rope.
For コウ, imagine a rope coiled tightly like a spring: coil -> コウ, and the rope is ready to be used.
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