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 "stuff", both of which derive 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. The common elements (hydrogen, oxygen, carbon and nitrogen) are named respectively Wasserstoff, Sauerstoff, Kohlenstoff and Stickstoff (literally: 'water-stuff', 'sour-stuff', 'coal-stuff' and 'smother-stuff', respectively) in German. Stoff 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. The following list refers to the World War II aerospace meanings if not noted otherwise.
A-Stoff (World War I): chloroacetone (tear gas)
A-Stoff (World War II): liquid oxygen (LOX)
B-Stoff: hydrazine or 75% ethanol / 25% water (used in the V-2)
Bn-Stoff (World War I): bromomethyl ethyl ketone, homomartonite (tear gas)
Br-Stoff: Ligroin extracted from crude gasoline
C-Stoff: 57% methanol / 30% hydrazine / 13% water / small amount of Catalyst 431 potassium-cuprous cyanide coordination complex
F-Stoff: titanium tetrachloride
K-Stoff: methyl chloroformate
M-Stoff: methanol
N-Stoff: chlorine trifluoride
R-Stoff or Tonka: 57% monoxylidene oxide / 43% triethylamine
S-Stoff: 90% nitric acid / 10% sulfuric acid or 96% nitric acid / 4% ferric chloride (The ferric chloride acted as a catalyst.)
SV-Stoff or Salbei (sage): 94% nitric acid / 6% dinitrogen tetroxide or 85% nitric acid / 15% sulfuric acid
(There was also an experimental variant of S/SV-Stoff containing 90% nitric acid and 10% perchloric acid)
T-Stoff (World War I): xylyl bromide tear gas
T-Stoff (World War II): 80% concentrated hydrogen peroxide / small amounts of 8-Hydroxyquinoline / 20% water used as hypergolic oxidizer with C-Stoff, or as monopropellant or power source with Z-Stoff
U-Stoff: dinitrogen tetroxide
X-Stoff: tetranitromethane
XU-Stoff: 70% (by weight) X-Stoff (tetranitromethane) / 30% (by weight) U-Stoff (dinitrogen tetroxide)
Z-Stoff: calcium permanganate / sodium permanganate / water