rope
綍 centers on a rope, specifically a thick rope used for pulling a coffin or bier in funeral contexts. The given meaning 'rope' is the core idea, with the kun reading hinting at its specialized use.
綍 combines 糸 (thread/silk) with 孛, which likely contributes the sound. The character originally referred to a thick rope, possibly made of twisted silk or plant fibers, used in funeral rites.
The left side 糸 suggests thread or cordage, while the right side 孛 looks like a complex knot or twisted bundle. Picture a thick rope woven from many threads, strong enough to pull a heavy coffin.
For フツ, imagine the sound of a rope snapping under tension: 'futs!' The sudden break cues フツ, and the rope is the core meaning of 綍.