the term "middle class" originated from the aristocratic ruling class of european feudalism

when people's place in society was determined by blood, by birth, there were two classes: peasants and nobility (and also there was clergy but there's always more detail, isn't there, so lets ignore the more fiddly categories...). As industrialization and market relations grew out of the early modern period, a funny thing started happening: there were people, born as peasants, who, through their property, started to amass wealth equal to (and often greater than!) the nobility. The nobles didn't like that. They looked down on this strange class that was caught in the middle of two worlds. Middle Class has historically referred to the Capitalists.

I know today the term just means a sort of vague gesture to some 'average of people'. But that's fucking useless. It only really acts to obfuscate the real defining characteristic of modern class; birthright has been replaced with the right of property (specifically property that generates a passive source of income for the owner). I highly advise to rail against, or at least avoid, the term "middle class". It just serves as a wedge to divide different levels of working class people from one another -- that's not a successful way to talk about and promote working class interests!