dig, turbid, exert
搰 centers on forceful physical action: digging into the ground, stirring something up until it becomes turbid, or exerting effort. The three meanings connect through the idea of working something with intensity.
搰 combines 扌 (hand) with 骨, which likely contributes the sound コツ. The exact historical development of the meaning is uncertain, but the hand component suggests manual action such as digging or stirring.
A hand 扌 working with bones 骨: imagine digging up old bones from the earth, stirring up dirt and making the water turbid, all requiring great exertion.
For コツ, picture digging with a hand tool and hitting a bone with a sharp *kots* sound: kots -> コツ, as you exert yourself digging.