It began as poisonous rotgut in Medieval Russia--Ivan the Terrible liked it, Peter the Great loved it--but this grain alcohol "without distinctive character, aroma, taste, or color" has become our uncontested king of spirits. Over a thousand brands fight for market share, shelved in glass skulls, Tommy guns, bulletproof bottles; flavored with pears, currants, chipotle; or quintuple distilled by Donald Trump. But it wasn't always thus. For 200...