(of flower petals) falling
簌 centers on the gentle, fluttering descent of flower petals, evoking a soft, scattered falling motion.
簌 combines 竹 (bamboo) with 欶, which likely contributes the sound. The exact historical development is uncertain, but the character is associated with the rustling or falling of petals, possibly evoking the sound of bamboo leaves.
Bamboo 竹 above a complex lower shape 欶: picture bamboo leaves drifting down like flower petals, soft and scattered.
For ソク, imagine a sock filled with flower petals falling gently: sock -> ソク, and the petals flutter down like the sock dropping.