to be grieved, sad
愪 centers on emotional distress: being grieved or sad. The meanings describe a state of sorrow or worry.
愪 combines the heart radical 忄 with 員, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound where the heart radical indicates an emotional state.
The heart radical 忄 beside 員 (which can suggest a round, full shape) evokes a heart weighed down by a heavy, round burden of sorrow. Picture a heart filled with grief, heavy and round like a stone.
For ウン, imagine a sad person letting out a low, mournful 'oon' sound: oon -> ウン, the sound of grief escaping from the heart.