The name saltpeter is derived from the Latin sal petrae and means ‘cliff salt’. Saltpeter is among the oldest, natural nitrogen compounds known to man. Today saltpeter is produced artificially. There are different types that in chemistry are designated as, for example, potassium nitrate, calcium nitrate or sodium nitrate.

Calcium nitrate is also known as ‘wall saltpeter’, since it often crystallized on the walls of stables or in caves. It forms a fine, hair-like coating on the walls that reminds one of mold. It can be brushed off. That is why this form of saltpeter is also called ‘brush saltpeter’. It can crystallize in caves and stalls because it is protected from rain showers there that otherwise would wash it away. Usually it is also present in normal soil. Nettles and elderberry indicate saltpeter-rich soil. The saltpeter is formed by bacteria from air and organic material, as, for example, from feces and urine.