Not tonight Joséphine
This is the supposed response by Napoleon Bonaparte when declining sex with Empress Joséphine.
There's no evidence whatsoever that Napoleon ever uttered these words. There's certainly no printed record of them in any language in his lifetime. The Oxford Dictionary of Quotations lists the phrase as early 20th century. The earliest reference that I can find is to a 1911 recording of a song with that name, composed by Seymour Furth and sung by Ada Jones and Billy Murray.
Why the phrase came to be coined isn't clear. Had it been earlier it might be plausible that it was a piece of anti-Napoleonic sentiment, which was rife in England a century before that song was penned. By the 20th century the strong feelings against Napoleon had abated. The couple were divorced, so it may be that it refers to some real or imagined event in Napoleon and Joséphine's life.