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 Words on the Move. John McWhorter joined us in 2016 for this interview, and we return to it here.