Cassis

Cassis: Cassis or Syrup of Cassis is a liqueur made of black currants. It shares its etymology with cassia, a plant genus that includes cinnamon, and other spices and medicinal herbs. Its appearance in this book about a American in French Indochina written by a British author most likely has one of two origins. First, Cassis is a French drink. Second, Agatha Christie made this a favorite drink of Hercule Poirot certainly introducing it to many English readers.

He made a noisy show of pulling out chairs and calling for the waiter, though all that activity could possibly produce at the Continental was a choice of beer, brandy and soda or vermouth cassis.