thighs, haunches, rump, share
脵 centers on the upper leg and hip area: the thighs, haunches, rump, or the share of a joint of meat from that region.
脵 combines the flesh radical ⺼ with 吴, which likely contributes the sound. The character is used for the thigh or haunch area.
The flesh radical ⺼ on the left points to a body part, and the right side 吴 looks like a person with a large lower body. Picture the fleshy thighs and rump of a person sitting.
For コ, imagine a child pointing at their thigh and saying 'co' as they learn body parts: co -> コ, and the flesh radical marks the spot.