Then your history teacher was ignorant, -ism comes from the greek -ismós which means “to take a stand in favour of” or “In the style of” it’s used to describe nearly all types of philosophical and religious ideas, art forms, schools of thought, etc etc

What she said is basically: “ignore every idea that exist cuz i say so” and you follow that blindly; please follow what you belive is good and true not what people tell you to follow otherwise you aren’t much more different than a blind sheep