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.
shi he (hexagram 21 of the I Ching: biting through)
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.