to rub, to crumple
捼 centers on applying pressure with the hands to distort or wear down a surface: rubbing, crumpling, or pressing into a softer shape.
捼 combines the hand radical 扌 with 委, which likely contributes a phonetic element. The exact historical development is uncertain, but the structure suggests a hand action related to the sound 委.
A hand 扌 pressing and twisting something soft like a piece of paper, represented by the right side 委 (which looks like a bent, crumpled shape), to rub or crumple it.
For ダ, imagine rubbing a crumpled piece of paper against a rough surface, making a dull 'da' sound: da -> ダ.