net radical variant (no. 122)
罒 is a radical variant of the net radical, used as a top component in characters related to nets, traps, or covering. Its standalone meaning is simply this radical shape.
罒 is a simplified top form of 网, which is a pictograph of a net. The modern form retains the net-like grid shape.
The four small boxes inside the outer frame look like the mesh of a net stretched across the top of a character.
For モウ, imagine a net catching a mow (as in mowing down) of fish: mow -> モウ, and the net scoops them up.