calm, quiet, move
憺 centers on a state of inner stillness: being calm and quiet. The meaning "move" seems contradictory and may be a rare or archaic usage; the primary idea is tranquility.
憺 combines 忄 (heart/mind) with 詹, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound related to a state of mind.
The heart radical 忄 beside 詹: imagine a heart that is so still it can hear the faint sound of a distant bell (詹 as a bell shape), bringing calm and quiet.
For タン, picture a calm tan-colored room where everything is quiet: tan -> タン, and the heart is at peace.
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miserable; pitiful; tragic; wretched; horrible; terrible
taxing one's ingenuity in devising something; agonizing over designing or creating something; making strenuous efforts to devise good ways and means to do something
terrible worry; extreme anxiety
taking great pains