Learning French: the origins and meaning of vendre la mèche

Do you know someone who cannot keep information under wraps and blabbers secrets at the first opportunity? 

You might describe them as having a tendency to vendre la mèche (to sell the fuse).

We look at the military origins behind this popular saying and share exactly how to use it like a native French speaker. 

What does vendre la mèche mean?

It literally translates as: to sell the fuse. The real meaning, however, has nothing to do with sales or electricity. 

This phrase actually refers to the idea of revealing something that should have been kept secret.

Synonyms include:

• Avouer - To spill the beans

• Révéler les secrets - To let the cat out of the bag

• Cracher / lacher le morceau - To give the game away

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What are the origins of vendre la mèche?

This expression has military connotations stemming from the mid-19th Century. 

Une mèche, in this context, refers to the fuse of a bomb or explosive device.

The original phrase was mixed with éventer la mèche (to vent the fuse or to fan the flames), due to the act of detonating a grenade or landmine and leaving the fuse in the open air to explode. 

This image became a metaphor for divulging a secret, and so the idiomatic definition was adopted. Some sources suggest the phrase was used to refer to soldiers who betrayed their own men by revealing strategic information or giving figurative ammunition to enemy armies.

It transformed into vendre la mèche, with use of vendre (to sell) having similar connotations to the idea of stabbing someone in the back or betraying their trust. 

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When do you say vendre la mèche?

You would say this when referring to something that should be kept a secret:

• J'organise une fête surprise pour mon mari et j'ai peur de vendre la mèche par erreur. - I am organising a surprise party for my husband and I am scared that I am going to let the cat out of the bag by mistake.

• Je ne peux plus faire confiance à ma collègue depuis qu'elle a vendu la mèche sur mon intention de démissionner. - I cannot trust my colleague any more since she spilled the beans about my plans to resign.

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To whom do you say vendre la mèche?

It is considered colloquial language and can be used with friends and family, mainly in spoken French.

It can sometimes come across as implying betrayal. Some people may take offence.