Moxie gets its bitter kick from the roots of wild yellow plants known as gentians.
Among the bitterest substances ever found on earth, gentians have been used by humans since ancient times as herbal remedies, according to Lena Struwe, a professor and gentian specialist at Rutgers University.
In Africa, gentians are used against malaria, in South America, they treat snake bites, and in Europe and Asia, gentians are mixed into digestives and aperitifs, such as Angostura.
No gentians are very toxic, but because of their bitterness they are seldom eaten by animals, which makes the plants easy to harvest.
"If you think grapefruits are bitter, this is much, much worse," Struwe said.
It was in the laboratory of a Lowell pharmacist, Dr. Augustin Thompson, where the beverage now known as Moxie was born. Thompson concocted a bitter potion with gentian root extract he had brought from South America.
Thompson patented the elixir and called it "Moxie Nerve Food," promoting spoonfuls of the medicine as a cure-all for common ailments in the late 19th century. It later took the form of a carbonated beverage.
There are various legends about Thompson's inspiration for naming his invention Moxie. Some stories say the drink was named after a Lieutenant Moxie, who discovered the active ingredient near the equator. But the elusive Lieutenant Moxie seems to have never existed. Others cite moxie plums or the Algonquin word "maski," which apparently means medicine. Either way, the bitter soft drink undoubtedly helped make the word "moxie" go mainstream, as a way to describe courage, nerve, spirit, and energy.