worry, agony, anger
懣 centers on a mind overwhelmed by intense negative emotion: worry, agony, or anger that fills the heart to the point of distress.
懣 combines 滿 (full, to fill) with 心 (heart/mind), suggesting a heart filled to the brim with emotion. The exact historical development is uncertain, but the phono-semantic structure is plausible.
The top 滿 means 'full', and the bottom 心 is the heart. Picture a heart so full of worry, agony, or anger that it feels like it will overflow.
For マン, imagine a man whose heart is completely full of worry: man -> マン, and his 心 is overwhelmed by 滿.
(pent-up) anger; indignation; resentment; irritation