comfortable, contented, peaceful
愔 centers on a calm, satisfied state of mind: feeling comfortable, contented, and peaceful.
愔 combines 忄 (heart/mind) with 音 (sound), likely suggesting a quiet, peaceful state of mind. The exact historical development is uncertain.
The heart radical 忄 beside 音 (sound) suggests a mind soothed by gentle sounds, leading to a comfortable, peaceful feeling.
For イン, imagine an inn where the heart is at peace: inn -> イン, and the quiet atmosphere makes you content.