Epazote (epazo¯tl is the Nahuatl word for the plant) gets its alternate name American wormseed from its long-standing and widespread use as a remedy for intestinal parasites. The practice apparently arose in Mexico and South America and was then passed northward, first to Native Americans and from them to white settlers. Its effectiveness (it paralyzes the parasites and then a strong laxative is taken to expel them) was recognized by its inclusion in the U.S. Pharmacopoeia from 1820 to 1947. Large plantings in Maryland in the nineteenth century supplied the essential oil (then known in commerce as Baltimore oil) to the pharmaceutical industry.