Loose Lips Sink Ships

Loose lips sink ships is an American English idiom meaning "beware of unguarded talk".

The phrase originated on propaganda posters during World War II. The phrase was created by the War Advertising Council and used on posters by the United States Office of War Information.

The most famous poster that helped popularize the phrase (pictured at right) was created for the Seagram Distillers Corporation by the designer Seymour R. Goff (also known by the pseudonym "Ess-ar-gee" or Essargee). This type of poster was part of a general campaign of American propaganda during World War II to advise servicemen and other citizens to avoid careless talk concerning secure information that might be of use to the enemy. The British equivalent used "Careless Talk Costs Lives", and variations on the phrase "Keep mum", while in neutral Sweden the State Information Board promoted the wordplay "en svensk tiger" (the Swedish word "tiger" means both "tiger" and "keeping silent"), and Germany used "Schäm Dich, Schwätzer!" (English: "Shame on you, blabbermouth!").

The gist of this particular slogan was that one should avoid speaking of ship movements, as this talk (if directed at or overheard by covert enemy agents) might allow the enemy to intercept and destroy the ships.

There were many similar such slogans, but "Loose lips sink ships" remained in the American idiom for the remainder of the century and into the next, usually as an admonition to avoid careless talk in general.

Some examples of use the phrase outside the World War II propaganda context are:

...
Wikipedia