whisper
聶 centers on quiet, intimate speech: whispering, murmuring, or speaking softly so only a close listener can hear.
聶 is composed of three 耳 (ear) components stacked together, suggesting many ears listening closely to a soft sound. The exact historical development is uncertain, but the repetition of 耳 strongly conveys the idea of attentive, quiet listening.
Three ears pressed together: one ear whispers, the other two listen intently. With so many ears so close, only a whisper is needed.
For ショウ, imagine a quiet show where the audience leans in with three ears to catch every whispered line: show -> ショウ.