The way we use language today is not the same as a couple of generations ago. If we used the word "cool" to describe something interesting to our great-grandparents, they probably would have wondered what caused the chilling.
Linguist/teacher/author John McWhorter makes the case that the English language is resilient, and that is why it changes over time. His most recent book on the subject is . John McWhorter joined us in 2016 for this interview, and we return to it here.