Morgan Meis at Slant Books:
It is startling and more than a little amusing to finally realize, or to have pointed out to you, as happened to me, that the word ‘dunce’, a not exactly au courant but certainly still, I think, recognizable word that basically means stupid, one who wears the dunce cap, that this word is, actually, a shortened form of saying that a person is like Duns Scotus, the medieval scholastic philosopher and member of the Franciscan order. Calling someone a dunce is calling them a Duns, a Scotist. Why one of the great minds of Western philosophy and theology would have become synonymous with stupidity is not immediately apparent. Something must have gone awry here.
In fact, the trajectory of word and meaning is not so hard to understand once one parses it out. Medieval Scholasticism, of which Duns Scotus was a great luminary, fell out of favor. Scotus’ once admired feats of logical daring began to look empty and pointless. Add to that the Protestant attack on the doctrines of the Church that Scotus did so much to defend intellectually and you get to the point where a person who was once called doctor subtilis, The Subtle Doctor, is now openly referred to as a dumb ass.
The question, though, and this is something I am still in the process of thinking through and which would require, I fear, rather too much reading of abstruse and difficult to love medieval works of philosophy, a task to which I devoted some time as a younger person studying philosophy while, at the same time, trying to bone up my medieval Latin, to varying degrees of success I should add, though I did get through quite a bit of Scotus’ work unraveling a couple of the trickier problems in what Aristotle means, exactly, by the words ‘being’ and ‘essence’.
More here.