"Stormtrooper" is from the German "sturm", meaning both "storm" and "assault" (although the latter was originally sturmangriff, literally "storm attack"). Lucas got it from the SA, or Sturmabteilung (roughly translated, "assault unit"), the armed nazi streetfighters in the early days of Hitler's regime.
So, before about 1925, "stormtroopers" meant soldiers specifically trained for attacking enemy positions (usually meaning they were better armed and possibly carried body armor), after that it began to mean "nazi paramilitary", which it remained until Star Wars.
Brian May was referring to the pulp image popularized in the 1960s and 1970s of female nazi disciplinarians wearing SS uniforms, catering to sexual fetishism.
Not Plutus but Apollo rules Parnassus