This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
爗 combines 火 (fire) with 曅, but the exact historical development and original meaning are uncertain.
With fire 火 beside the complex 曅, imagine a bright, blazing flame, but the exact meaning is unclear.
For ヨウ, picture a glowing ember: yo! -> ヨウ, as if calling out to the bright fire.