grieving
慱 centers on deep sorrow or grieving. It expresses a heavy, heartfelt sadness.
慱 combines 忄 (heart/mind) with 專, which likely contributes the sound and may relate to concentrated or heavy feelings. The exact historical development is uncertain.
The heart radical 忄 beside 專 suggests a heart weighed down by concentrated sorrow. Picture a heart so heavy with grief that it can't be lifted.
For タン, imagine a person grieving so deeply they can only manage a tan (as in a light brown color) of energy, their heart too heavy to feel bright. Tan -> タン.