OK, I have a theory. What if doughnuts, Aka nuts of dough, are not actually the doughnuts themselves, but merely the fleshy rind harvested when the true nut is popped out of the middle of the dough fruit. Over time, people decided that the discarded husk was also edible and actually larger than the original fruit. Thus, they no longer enjoy the “nut” of the fruit, but rather, its rind, but having no new word for the husk, simply called it a doughnut as well. Eventually the two terms were conflated and the original meaning lost, until the original dough-nut was designated the dough-nut “hole”, thus attributing the absence of the nut in relation to its whole as the name of the original nut itself. It’s a linguistic gold mine, full of many twists and turns.