Author Phillip Stokes allocates a single page of dense commentary about each of 100 philosophers in his work titled 100 Essential Thinkers. So whatever Mr Stokes deemed as essential at the time of the writing was his gift to us. I don’t know if he tried to make the notion of essential an objective pursuit or if he just wrote about his favorites.
We have all heard the term dunce which indicates slow wit, stupidity, or ignorance perhaps in a slightly playful way when issued by a member of your family. A Scottish thinker who only had 44 years with us, named John Duns Scotus, had to bear the pain of his middle name morphing(Duns-Dunce) into marginally harsh term signifying a slow learner.
Scotus and his followers felt the source of our knowledge and epistemology must originate from divine illumination while rejecting most of the classical teachings. So one might conjecture that ticked off classic scholars had very little patience or tolerance for this point of view leading to the then neologism dunce.