Falernum is a sweet syrup that originated in Barbados. It is a sweet syrup that can have a variety of different ingredients. There are countless recipes for falernum, but it generally contains ginger, cloves, and limes. Sometimes it is alcoholic and sometimes it isn't. You can make your own falernum or buy a commercially available one. Some of the most common brands are B.G. Reynolds and John D. Taylor's Velvet Falernum.