If you've had a "real" gin-and-tonic then you've tasted quinine water. That's the tonic.
Quinine is an old drug, named for the tree from whose bark it was first obtained. But whence the name of the tree? If this account is accurate, it's an interesting story in its own right:
From http://www.a1b2c3.com/drugs/gen001.htm...Quinine was isolated from the bark of the cinchona tree by the French chemists Joseph-Biename Caventou and Pierre-Joseph Pelletier in 1820, 200 years after the bark was introduced into Europe for the treatment of malaria. The Peruvian Indians had recognized for years the value of the quinquina tree for treating feverish patients.
Some historians believe that malaria was imported to South America by the conquistadores and their African slaves. A persistent story exists about Dona Francisca Henriquez de Ribera, wife of Count Chinchon, the Spanish viceroy of Peru. She fell ill with malaria (the "tertians" variety with chills and fever that recur every third day) and was cured by an Indian healer who gave her the bark.
In gratitude for the cure, the countess distributed the bark to other patients in Lima and thus alerted Spanish physicians to its clinical potential. The great Swedish botanist Linnaeus (Carl von Linne, 1707-1778) later called the tree cinchona in honor of Countess Chinchon, misspelling her name in the process.
It is improbable that the countess persuaded Spanish doctors to use the bark because she died in Cartagena, Colombia, in 1641, while returning home. Because the antimalarial value of cinchona became more widely recognized while supplies of the bark fell short of demand, the cost of the powder was often matched by its weight in gold.
The cinchona tree grows wild in the sub-Andean jungles, and a number of European powers tried to transplant it to other tropical places. Peruvian officials realized what a gold mine these trees represented and strictly prohibited their export.
A British attempt to smuggle some trees out of Peru failed, but two Dutch adventurers managed to get a few specimens across the border. The stolen trees were taken to Java and became the ancestors of later improved plantation trees that, before 1940, furnished 97% of the world's supply of quinine.
The inaccessibility of Java-and of Sri Lanka, where a few smaller plantations existed-became a source of worry for European drug factories that were the principal sources of pure quinine. This concern was felt acutely by German manufacturers in World War I, when they were unable to supply European colonies in Africa with the drug.
In World War II, British and American suppliers also were cut off from their Oriental sources of quinine when the Japanese occupied Java and Malay.
In both instances, the drug shortage stimulated intensive research to surmount this handicap, and the resulting new compounds are almost the only effective synthetic antimalarials we have today. Nevertheless, quinine has kept a modest but important and inexpensive place in antimalarial treatment
--from Understanding Medications..., by Alfred Burger
Just to make it useful: "they" say that quinine water, or just plain quinine, is also good for relieving the leg and foot cramps that most of us get at night from time to time.