dissatisfaction, grudge
怏 centers on a lingering feeling of discontent: dissatisfaction or a grudge that persists.
怏 combines 忄 (heart) with 央, which likely contributes the sound and may suggest a central, lingering feeling. The exact historical development is uncertain.
The heart radical 忄 beside 央 (center) suggests a feeling stuck in the center of your heart: a grudge or dissatisfaction that won't go away.
For オウ, imagine someone holding a grudge saying 'Ow!' every time they remember the slight: Ow -> オウ, and the heart 忄 keeps the pain central.
discontented; unhappy