dunce

The word comes from John Duns Scotus, a Scottish thinker who died around 1308. His followers later resisted the new ideas of the Renaissance, and by 1530 their name had curdled into a word for someone clinging stubbornly to old, outdated learning.

It began narrowly, aimed at those rejecting new knowledge, but widened over time to describe any person thought simply stupid.

The facts given don't point to any surviving cognate — 'dunce' stands alone here, a name worn down into an insult.