trousers, breeches leggings, drawers
絝 centers on lower-body garments: trousers, breeches, leggings, or drawers. The meanings all refer to types of pants or legwear.
絝 combines 糸 (thread) with 夸, which likely contributes the sound. The thread radical suggests a garment made of fabric, fitting the meaning of trousers or leggings.
The left side 糸 is thread, and the right side 夸 looks like a person with wide legs. Imagine sewing thread into a pair of trousers that fit loosely around the legs.
For コ, picture a tailor sewing trousers while humming a little tune: "Co-co-co..." The sound コ echoes the humming as the thread goes through the fabric.