good looking, to play as one pleases
媱 centers on a carefree, pleasing appearance: being good-looking and playing as one pleases. The two meanings connect through the idea of an attractive, unconstrained demeanor.
媱 combines 女 (woman) with 䍃, which likely contributes the sound and may relate to a carefree or attractive quality. The exact historical development is uncertain.
A woman (女) beside 䍃, which looks like a container with something spilling out, suggests a free-spirited, attractive person playing as she pleases.
For ヨウ, imagine a good-looking person playing freely and saying 'Yo!' to everyone: Yo -> ヨウ, capturing the carefree, attractive vibe.