night watch, rake
掫 centers on guarding or gathering: keeping watch at night, or raking things together. The two meanings are not obviously connected, but both involve a hand action—either holding a protective stance or pulling things in.
掫 combines 扌 (hand) with 取 (take). The exact historical development is uncertain, but the hand component fits the meanings of guarding or raking.
A hand 扌 beside 取 (take) suggests a hand taking action: either holding a weapon to keep night watch, or raking things together like a hand gathering leaves.
For ソウ, imagine a guard raking the ground during the night watch, making a soft 'sow' sound as the rake moves: sow -> ソウ.