Theriac

Theriac or theriaca was a medical concoction originally formulated by the Greeks in the 1st century AD and widely adopted in the ancient world as far away as China and India via the trading links of the Silk Route. It was an alexipharmic, or antidote, considered a panacea, for which it could serve as a synonym: in the 16th century Adam Lonicer wrote that garlic was the rustic's theriac or Heal-All.

The word theriac comes from the Greek term θηριακή (thēriakē), a feminine adjective signifying "pertaining to animals", from θηρίον (thērion), "wild animal, beast". The ancient bestiaries included information—often fanciful—about dangerous beasts and their bites. When cane sugar was an exotic Eastern commodity, the English recommended the sugar-based treacle as an antidote against poison, originally applied as a salve. By extension, treacle could be applied to any healing property: in the Middle Ages the treacle (i.e. healing) well at Binsey was a place of pilgrimage.

Norman Cantor observes that the remedy was homeopathic in its supposed effect, following the principle of "the hair of the dog," in which a concoction containing some of the poisonous (it was thought) flesh of the serpent would be a sovereign remedy against the creature's venom: in his book on medicine,Henry of Grosmont, 1st Duke of Lancaster wrote that "the treacle is made of poison so that it can destroy other poisons". Thinking by analogy, Henry Grosmont also thought of theriac as a moral curative, the medicine "to make a man reject the poisonous sin which has entered into his soul." Since the plague, and notably the Black Death, was believed to have been sent by God as a punishment for sin and had its origins in pestilential serpents that poisoned the rivers, theriac was a particularly appropriate remedy or therapeutic. By contrast, Christiane Fabbri argues that Theriac, which very frequently contained opium, actually did have palliative effect against pain and reduced coughing and diarrhea.

...
Wikipedia