Put a sock in it

We all know the phrase ‘Put a sock in it’, used to mean ‘be quiet’, but its origins are vague. The imagery behind the phrase is that putting a sock in whatever was causing the noise would quieten it down. But what that thing was isn't known for certain. It may simply have been one’s mouth but more attractively there are suggestions that this may have been the horn of an early gramophone.

The earliest example of it in print that the Phrase Finder can find is a definition of the term in the weekly literary review The Athenaeum 1919:
"The expression ‘Put a sock in it’, meaning 'Leave off talking, singing or shouting'."
The fact that an erudite publication saw fit to define the term suggests it was recently coined in 1919.