embers
燠 centers on the glowing remnants of a fire: embers, the hot coals left after flames die down.
燠 combines 火 (fire) with 奧, which likely contributes the sound and the idea of something deep or interior, suggesting the inner heat of embers.
The left side is fire 火, and the right side 奧 looks like a deep, enclosed space. Picture a deep fire pit where only glowing embers remain.
For ウ, imagine the sound of a soft wind (ウー) blowing over the embers, making them glow brighter: ウー -> ウ.