Literal Translation
A story to make you sleep upright
Actual Meaning
A tall tale, an unbelievable story
Etymology
This expression can be found in the 17th century with the same meaning as today. There’s no juicy story, it’s simply because dreaming happens when we’re asleep, and dreams belong to an unreal world. Sleeping standing up is like being in a dream, but this time while being wide awake. So when we say that a story is ‘à dormir debout’, we mean that it’s not real, that it belongs to the world of dreams.