Here's how the theory goes:
* After the Napoleonic Wars (1803-1815), many Russian soldiers stayed in Paris. They frequented small, simple taverns where they could get food and drink quickly.
* These taverns were known as "bistros" because they served food and drink "bystro" (quickly).
* The word eventually became adopted into French, and from there into English.
It's worth noting that there are other theories, including:
* The word might come from the French word "bistre," which refers to a dark brown color. This theory suggests that the term might have referred to the dark, smoky interiors of these small taverns.
* The word might be a shortened version of "bistouri," the French word for "scalpel." This theory suggests that the word might have been used for taverns that were particularly crowded and chaotic, like a butcher shop.
While the true origin remains a bit of a mystery, the "bystro" theory is the most common and widely accepted explanation.