During World War II, Germany fielded many aircraft and rockets whose fuels, and oxidizers, were designated (letter)-Stoff.
In German, Stoff means roughly the same thing as English "material", "substance" and through its translation as a calque noun from German to English as "stuff", the German form derives ultimately from the Old French word estoffe (meaning cloth or material). Stoff has as broad a range of meanings, ranging from "chemical substance" to "cloth", depending on the context. It was used in chemical code names in both World War I and World War II. Some code names were reused between the wars and had different meanings at different times; for example, T-Stoff meant a rocket propellant in World War II, but a tear gas (xylyl bromide) in World War I. Currently, this list refers only to the World War II, aerospace meanings.