What Part of “No, Totally” Don’t You Understand?

English continues to evolve. I noticed this construction several times today.

“No, totally.” “No, definitely.” “No, exactly.” “No, yes.” These curious uses turn “no” into a kind of contranym: a word that can function as its own opposite. Out of the million-odd words in the English language, perhaps a hundred have this property. You can seed a field, in which case you are adding seeds, or seed a grape, in which case you are subtracting them. You can be in a fix but find a fix for it. You can alight from a horse to observe a butterfly alighting on a flower. —The New Yorker.