Treacle: A medicinal compound once in wide use as an antidote to poisons. Treacle was a kind of salve. It was reputed to be a remedy against venomous bites in particular and against poisons in general. It also came to be considered a "cure" for cancer.
The word "treacle" descends from the Greek "theriakos" (of a wild animal) and "therion" (a wild animal). Because wild animals may bite, these words gave rise to "theriake" meaning "antidote against a poisonous bite." The Romans borrowed "theriake" as "theriaca" and the word eventually entered Middle French and, in time, Middle English as "triacle."
Treacle today also refers to molasses or a blend thereof with sugar. By extension, treacle is figuratively something very sweet, too sentimental, cloying.