old cotton, tangled hemp, raveled silk, vague, confused
縕 centers on tangled, disordered fibers: old cotton, knotted hemp, or raveled silk. The abstract senses of vague and confused extend naturally from the idea of something messy and unclear.
縕 combines 糸 (thread) with a phonetic component that historically contributed the sound ウン/オン. The exact origin of the right-side component is uncertain, but the character likely expressed tangled or old fibers.
The left side is thread 糸. The right side looks like a jumble of shapes (人, 口, 皿) all tangled together. Picture a messy pile of old cotton and knotted hemp threads that is impossible to untangle.
For ウン, imagine the sound of a confused person groaning 'un...' while staring at a hopelessly tangled ball of old cotton: 'un' -> ウン.