timid, apprehensive
愞 centers on a fearful, hesitant state of mind: being timid or apprehensive about what might happen.
愞 combines 忄 (heart/mind) with 耎, which likely contributes the sound and may relate to softness or weakness, fitting the timid meaning. The exact historical development is uncertain.
The heart radical 忄 beside 耎 suggests a heart that is soft and yielding. Picture a timid person whose heart shrinks back at the slightest pressure.
For ゼン, imagine a timid Zen monk who is too apprehensive to ring the bell: Zen -> ゼン, and his fearful heart holds him back.