As one who always has a bottle of it around, the "Cassis" referred to is normally in the syrup form made from black cuurents in Burgundy since medieval times and non-alcoholic ( I love it over vanilla ice cream or just a little mixed with soda or even Sprite)

The Cassis liqueur is "Creme De Cassis" and is the basis of the aperitif Kir ( named after the mayor of Dijon in the 40s - Felix Kir) when mixed with white wine.

mIke