Socialism
Those terms were not defined at the time of the middle ages, the “age of nobility”, which I specifically stated to be excluded.
I have a reason for this - the terms Communism, Socialism, or Fascism are, these days, very loaded, and will just be rejected as “hate speech”.
But, if you point out the parallels to “nobility and peasants”, leftist apologists don’t dismiss your argument and actually look at what is going on.