According to the Vinegar Institute, the useful stuff was probably discovered by accident (most wine drinkers know what happens when you leave a bottle sitting around too long). In fact the word vinegar comes from a French translation for "sour wine." Over the centuries vinegar has been produced from many stocks, including molasses, dates, sorghum, fruits, coconut, honey, beer, maple syrup, potatoes, beets, grains and more. But the principle is the same: you get acetic acid (a.k.a. vinegar) after first fermenting natural sugars to alcohol, and then fermenting again.