the blaze of fire, dazzling
熀 centers on intense, brilliant light or fire: a dazzling blaze that overwhelms the senses.
熀 combines 火 (fire) with 晃 (bright, dazzling), suggesting a blazing, dazzling fire. The exact historical development is uncertain, but the component relationship is clear.
Fire 火 on the left and dazzling brightness 晃 on the right: imagine a fire so intense it creates a blinding, dazzling blaze.
For ヨウ, picture a dazzling fire that makes you say 'Yo!' in awe: Yo -> ヨウ, as the blaze lights up everything.