to shout, roar, terrify, swiftly
譹 centers on loud, forceful vocal expression: shouting, roaring, or making a terrifying noise. The "swiftly" sense is less common and may be a separate application, but it can be understood as a sudden, startling outburst.
譹 combines 言 (speech) with 豪, which likely contributes both sound and the idea of powerful, unrestrained force. The exact historical development is uncertain, but the phono-semantic structure is plausible.
Words 言 spoken with the force of a mighty 豪 warrior: imagine a powerful shout that terrifies and roars through the air.
For コウ, picture a mighty shout echoing through a vast hall: the sound "koooh" reverberates, matching コウ.