The admonition, “Put a sock in it,” meaning keep quiet, comes from the time of the earliest wind-up phonographs in which the sound emerged from a horn.
These early acoustic record players didn’t have electronic controls or any muting device to raise or lower the volume, and so the only way to soften or muffle its sound was to stuff something into the horn.
A sock was the perfect size, and so to lower the volume they would “put a sock in it.”
