pretend, crouch
蓌 centers on deceptive lowering: pretending or feigning, often by crouching or assuming a false humble posture.
蓌 is a rare character. It combines the grass radical 艹 with 夎, but the historical origin and the role of 夎 are uncertain. The modern form may be a simplification or variant, but no clear older form is widely established.
Under the grass 艹, imagine a person 夎 crouching low to pretend they are not there. The hidden posture captures both pretending and crouching.
For サ, picture someone crouching in the grass and whispering 'sah' to signal a pretend ambush: sah -> サ.