It has been suggested that the French word “bistrot” dates back to 1812 and the invasion of Russia. Whilst on campaign, the French hussars of the Grande Armée took to frequenting the taverns along the route, in search of food and a bit of fun. The bar's Cossack clientele, keen to avoid the company of the incoming foreign soldiers, would hasten to finish their drinks. The Russian word “bistra” – meaning “quick” – would fill the air, and the French soldiers, with little understanding of the language of Tolstoy, took to referring to these bars as places where they say “bistra”. This evolved into “bistro”, and subsequently “bistrot”, following the Grande Armée's return to France, and was used to refer to cafés, bars, and places where drinks were consumed.
A second, related etymology has also been suggested: this time it is the Cossacks drinking in Parisian bars during the occupation of Paris (March 1814) who took to saying “bistra” whilst they were waiting impatiently to be served.