The first "fast food": The word "bistro" for a small restaurant comes from the time of the Russian occupation of Paris in 1814. Russian soldiers would call "bistro, bistro"--which means "fast, fast", in other words, hurry up--to the waiters of French taverns. The term finally stuck and became the name of a quick-service restaurant.
I'm sure that the french had no idea what "bistro" meant, but in either case grew popularity (for reasons unknown) and later the name migrated into other countries as a fast food restaurant name. Even back in Russia people opened up Bistro's, pronouncing it differently than the original Russian word. This one had a tiny French accent.