Botanical name: 

Horehound, Marrubium vulgare, is indigenous to Europe, but has been naturalized in America, where it is now very common. Its use as a bitter decoction led to its early introduction into domestic medicine, as well as to its popular use as a bitter flavor in candy. Probably the well-known horehound candy may be cited as a domestic medicine that has become popular as a confection. The date of the use of horehound as a sweetened domestic tea must have been very early in the records of European home medication.

The History of the Vegetable Drugs of the U.S.P., 1911, was written by John Uri Lloyd.