What does "put a sock in it" mean — and why is it funny?

informal, British

Meaning

A blunt request for someone to stop talking or be quiet.

Where it comes from

British slang from the early 1900s. A popular theory ties it to early gramophones, which had no volume knob — listeners stuffed a sock into the horn to muffle the sound.

Why it is funny

It treats a person like an over-loud machine. The image of literally jamming a sock into someone's mouth to turn their volume down is rude and ridiculous at the same time, which is exactly why it stings less than 'shut up' and lands as a joke.

Used in a sentence

"Put a sock in it — I'm trying to sleep."