Pipe Down

A naval pipe call ordering off-duty personnel below or signalling quiet and lights out.

Orders aboard naval ships were traditionally transmitted by distinctive notes sounded on a boatswain’s call. “Pipe down” came to be associated with the end of the day’s activities and the requirement for silence.

In everyday speech it now means to become quiet or stop talking. The modern command preserves the naval wording but is used far beyond a shipboard routine.