Dubonnet is a wine-based aperitif, fortified with herbs, spices, and quinine, which originated in France.
It was created originally as a novel way of getting members of the French Foreign Legion to ingest quinine, a defence against malaria.
As the text suggests, it was considered quite a sophisticated drink in the 1950's and 60's. In later years its popularity declined, although it has recently undergone something of a retro revival.
It is a key ingredient in many cocktails.