On May 13th, 1806, the Balance and Columbian Repository published the first definition of a "cocktail." “Cock-tail is a stimulating liquor, composed of spirits of any kind, sugar, water, and bitters…”. This looks remarkably like the ingredients of an Old Fashioned!
A little thing called Prohibition raised a generation who had no reference for the art of cocktails that had existed in the United States for over 100 years. In the 1800s one would just order a Whiskey Cocktail or Gin Cocktail. How to make one was common among barkeeps. But after Prohibition, those behind the bar weren’t really familiar with the old ways. Imagine an old timer coming back to the bar who had grown up in that former time and asking for a Whiskey Cocktail. The bartender may have been confused, not knowing what this guest would like him to make with the Whiskey. Perhaps the patron then listed off the ingredients and how to build it. “You know! Make it the old fashioned way. The way I used to get!” Today, the Old Fashioned is a whiskey cocktail but "old fashioned" is actually a way of preparing a "cocktail" and can be delicious with any type of spirit.