Distilling was a fairly common practice in 18th century farming communities; if for no other reason than to make full use of the harvested corn.
Why distill it? A major reason was transportability. Wagons overflowing with ears of corn were considerably larger and less convenient than moving a barrel of whiskey.
A factor that lead to the spread in popularity of Kentucky whiskey was its location near the Ohio River.
This distilled clear juice was stored in barrels, labeled “Old Bourbon Whiskey,” and sent down the River bound for New Orleans. “Old Bourbon” referred to the original Bourbon County, VA area that was now KY.
The corn whiskey immediately became a hit with the New Orleans French crowd. The sweet taste had a curious resemblance to their beloved cognac and a nice contrast to the northern rye whiskies that were commonplace at the time.
Bourbon also had namesake ties to the France, and likely played in the Sprits favor in spreading the popularity of the whiskey. Over time the “Old Bourbon” was eventually shortened to “Bourbon.”
As the popularity for the sweet spirit spread, all American corn-based whiskies came to be known as “Bourbon.” It wasn’t until many years later that formal requirements were established to differentiate Bourbon from all other Whiskies.