Why is the ninth month called September?
1906, from French bistro (1884), originally Parisian slang for "little wineshop or restaurant," of unknown origin. Commonly said to be from Russian bee-stra "quickly," picked up during the Allied occupation of Paris in 1815 after the defeat of Napoleon; but this, however quaint, is unlikely. Another guess is that it is from bistraud "a little shepherd," a word of the Poitou dialect, from biste "goat."
A restaurant or cafe
[1940s+; fr French]