means To make or become quiet, or a state of silence — often used as a soft command to stop someone talking or crying.

from An imitative word, born from the very sound it asks for — that soft 'shh' breathed across the lips to soothe a child or calm a crowd. English has had 'husht' and 'hush' since the late Middle Ages, and like 'shush' and 'hist' it belongs to a family of words that don't so much mean silence as enact it. Some link it to a Middle English 'huisht' or 'whist,' but the deepest root is simply the human instinct to answer noise with a quieting breath.