to whisper. to blame to slander
咠 centers on quiet, often harmful speech: whispering secrets, blaming, or slandering someone behind their back.
咠 combines 口 (mouth) and 耳 (ear), suggesting speech directed at the ear, such as whispering or slander. The exact historical development is uncertain, but the component relationship is clear.
A mouth 口 right next to an ear 耳: someone leaning in to whisper blame or slander directly into the ear.
For シュウ, imagine a person whispering 'shh' into an ear, then saying 'you': shh-you -> シュウ, as they slander someone quietly.