cocktail

   1. obsolete

   a prostitute

   Possibly a pun, also referring to cockatrice, a prostitute, from the fabulous serpent which killed by its glare:

    Such a coxcomb as that, such a cocktail. (Thackeray)

   2. a mixture of alcohol or illegal narcotics

   We have a choice of derivations, some more far-fetched than others. We can rule out the 'six-oared boat used by Kentish smugglers' and derivation from the Krio koktel, meaning a scorpion. In Yorkshire it once meant a flaming tankard of ale, which is getting closer.

   The obvious candidate is the French coquetel, from the feather used to stir the drink, but I still stay with the Aztec xoc-tl, named from the maiden Hochitl who introduced to the king a concoction devised by her father, thereby winning his heart and immortality. Commoner in America than in Britain, where it tends to be refer specifically to a drink based on a spirit without a generic meaning of intoxicants:

    They had been having cocktails every night. (M. McCarthy, 1963)

   Whence cocktail bars, hours, lounges, and the like.