Vinegar has been used as a health tonic since the time of Hippocrates, in fact, Hippocrates himself recommended it to wash out ulcerated wounds with (ouch!!) in order to keep bacteria at bay and allow the wound to heal. Prior to the invention of oral hypoglycaemic agents (metformin et al) diabetes was controlled by vinegar teas.
Although vinegar comes from the French for sour wine (vin aigre) it can be made from pretty much any liquid which contains a source of carbohydrates, as the sugar is fermented into alcohol then oxidised into vinegar by Acetobacter a specialised bacteria which forms acetic acid, hence its name.
Some examples of foods which have been used to produce vinegar include: apples, beer, beets, berries, coconut, dates, grains, grapes, honey, malt, maple syrup, melons, molasses, sorghum, pears, potatoes, wine and whey.
Although why anyone would want to turn something as delectable as maple syrup into vinegar is beyond me!