fear, worry over, fill, satisfy, calm, at ease, tranquil
惵 centers on an emotional state that can swing between inner unease and quiet contentment: fear and worry on one side, and being filled, satisfied, calm, or at ease on the other. The meanings are not a single tight cluster, but they share a focus on the heart's condition.
惵 combines the heart radical 忄 with 枼, which likely contributes a phonetic role. The exact historical development of the meaning range is uncertain.
The heart 忄 beside 枼 (a tree with leaves) suggests a mind that can be either rustled by fear like leaves in the wind, or settled and calm like a tree at rest.
For チョウ, imagine a person named Chou sitting under the 枼 tree, feeling completely at ease: Chou -> チョウ, and the heart is tranquil.