Tomber des nues could be translated by “to fall from the naked women”. However, nues in this idiomatic expression has nothing to do with women. The word nues refers to the clouds. So tomber des nues, literally “to fall from the clouds” means to be extremely surprised or to be dumbfounded.
In the 17th century, the expression was used to refer to someone arriving unexpectedly, like someone who would fall from the sky. The meaning then evolved to express the surprise.