My understanding was it was for the glass set on the table to spit the shot from birds when consumed.
Seems like a bowl would be more appropriate ... wider opening ...
The most popular origin story is that the shot glass originated in the Western saloons of the Old West. The story explains that the cowboys of the old west would trade a cartridge (bullet plus powder and primer encased in brass) for a small amount of alcohol. One problem with this story is that, even if true, your average old west saloon would not be able to “commission” the creation of a new style of glass to fill this purpose but– they had a glass to measure an ounce of whiskey, yet even today many bars do not stock shot glasses; they serve shots in ordinary whiskey glasses. Another problem with this origin story is the economics of such a trade are such that it would never happen. Alcohol sold for much more than a single cartridge, however some cartridges held more powder or lead as in the difference between a pistol and a rifle, but then again, some rifles used pistol cartridges as in the 45 long Colt.
Another origin story is that a “shot glass” was a glass used at the dinner table to place any “shot” left in your meat that you would find during a meal. However, people were shooting their food with shotguns for hundreds of years before the shot glass was born.
There may have been a “shot glass” for this purpose, but the shot glass did not come from it.
So bottom line - I like the romanticized western cowboy version better.
/r/Jane