Etymology

In the United States, carbonated water was known as soda water until WWII due to the sodium salts it contains, which are added as flavoring and acidity regulators to mimic the taste of natural mineral water. During the Great Depression, it was also called two cents plain, a reference to its being the cheapest drink at soda fountains. In the 1950s terms such as sparkling water and seltzer water gained favour. "Seltzer water" is identical with carbonated water if it contains no additives or flavourings. The term seltzer water is a genericized trademark that derives from the German town Selters, meaning "water from Selters", which is renowned for its mineral springs. .[3] where naturally carbonated water has been commercially bottled and shipped into all parts of the world at least since the 18th century.[4]

In many parts of the U.S., "soda" has come to mean any type of sweetened, carbonated soft drink, such as cola.