“Mum's the word”in other languages

Same idea, different pictures

English mum is the sound made with closed lips; Shakespeare already has “give no words but mum”. French sews the mouth shut, motus et bouche cousue, with motus a mock-Latin word made from mot. Polish puts a padlock on it, trzymać buzię na kłódkę.

Italian fills the mouth with water, acqua in bocca, with a popular story about a gossip told by her priest to keep water in her mouth whenever she felt the urge to talk. Romanian is silent like a pig in the cornfield, a tăcea ca porcul în păpușoi: quiet because it's guilty.