As I’m freshly back from a week’s holiday in Scotland, I was amused to come across contrast shower, which means to alternate cold and hot showers in order to speed up recovery after intense physical exercice. Indeed, the French translation is douche écossaise (Scottish shower). This is what Expressio has to say about this expression (simplified translation):
Since the middle of the 19th century, the Scottish shower is a shower which alternates cold and hot water to create a strong contrast.
By extension, since the middle of the two world wars, it refers to successions of strongly contrasted events, situations, actions, words i.e. reversals of situations.
But why Scottish? It’s hard to find a detailed explanation of the origin of this expression, apart from an often repeated suggestion that it could come from a form of hydrotherapy used by the Scots.
The Isle of Skye was stupendously beautiful, by the way.