When you start looking through vintage cocktail books, one thing you'll quickly notice are the names of obscure ingredients. Now, some of these ingredients are still in production—you might have to hunt a while; you might even need to have a friend bring a bottle home from overseas. But others are truly defunct, no longer made. What did they taste like? How were they made? Here's our guide to a few bitters, liqueurs, and cordials that truly have disappeared...and a few that are being revived by upstart brands.