eat seeds, reproach, loquacious
嗑 centers on speech and consumption: talking excessively (loquacious), reproaching with words, or eating seeds by cracking them open with the mouth. The meanings are loosely connected through the mouth radical 口.
嗑 combines 口 (mouth) with 盍, which likely contributes the sound. The exact historical development of 盍 is uncertain, but the character is associated with speech and oral actions.
A mouth 口 that is always moving, like someone cracking seeds, chattering nonstop, or scolding others. The right side 盍 looks like a container with a lid, suggesting the mouth is constantly opening and closing.
For コウ, imagine a person talking so much they start to cough: cough -> コウ, and their loquacious mouth keeps going.