I didn't know this bit: 'Back when English was a four-form system, it, too, had a si—a word used specifically to contradict negative statements. That word was

I didn't know this bit: 'Back when English was a four-form system, it, too, had a si—a word used specifically to contradict negative statements. That word was “yes.” To affirm positive statements, you used “yea”' (Then continues about the similar no / nay.) Anyway, I'm surprised the writer did not work in the joke about the lecturer saying: "As you know, a double negative becomes a positive, but the reverse does not happen." Voice from the back of the room: "Yeah, yeah ..."