Alcohol evaporates at roughly 175 degrees F.
This is the key fact that one needs to know to understand the basic premise of distillation. For if you have a fermented beverage (say, a nice wine) and you wanted to boil it, the alcohol within the beverage would start boiling off before the water of the beverage would. If you could only muster a very small fire, and could not get the temperature of the wine above 200 degrees F, then you would eventually boil off most of the alcohol and leave a fair amount of the rest of the liquid behind. This undoubtedly happened so often in the past that no one specific person can say “I’ve discovered the art of removing the alcohol from wine/sake/beer/cider!”. We don’t know who discovered this act any more than we can say who discovered fire.
But removing alcohol from fermented beverages is not the same as distilling. For distillation to occur, one must separate and collect the various liquids from the initial composition.
It wasn’t until someone had the bright idea to put a lid with a condensation collector upon the pot of liquid that was being heated that distillation actually became a viable process. So using the example above, the wine would heat to 200 degrees F, and the steam from the alcohol would rise to the top where it would collect on the top of the lid. Condensation would form and drip either back down into the wine, or into a tube or funnel that had been attached to the lid. In that case, the condensation would drip down the tube or funnel and deposit itself in another container. Voila! The Alcohol had been separated from the wine and someone had created a rough form of brandy.
Of course this is but one of many ways of distillation. It’s also likely the first form of distillation had nothing to do with heat. Rather, it had to do with freezing. Alcohol freezes at a much lower temperature (-117 degrees C) than water (0 degrees C). It’s not beyond the realm of probabilities that people placed their sakes/ciders/beer/wine out doors on a cold winter’s night, only to wake up to find that the alcohol within their fermented beverage was still in liquid form, while everything else was a solid chunk o’ ice.
Whether it was through heat, freezing or some other manner, when it comes to liquor and spirits, it means that we’re talking about the alcohol that has been extracted from some version of a fermented liquid.
(graphic swiped from Wikipedia)