Apr 10, 2020 · Russian rocket engineers nickname it "heptyl". Why was this name chosen , especially when it means a compound with 7 carbon atoms , and UDMH has only two? Addendum: As several commenters also seem to believe, my suspicion is that the name was chosen as a codeword during the Cold War to deceive enemies.

Heptyl: This is how Russians refer to UDMH, aka Hydrazine. Hydrazine is very toxic and dangerous for humans to be around, and Kazakhstan has had hydrazine rained down on it many times when rockets have failed. It's nasty but no human deaths have been attributed to it as a result due to the remoteness of the region.

$\begingroup$ A great and really funny story of propellants research is John D. Clark. Ignition! (1972) See, in particular, the "Hunting of the Hypergol" chapter.