A few years ago I was backpacking around Asia met some friends in northern Vietnam. We were 6 or 7 people so we just rented out a dorm room in a hostel. There were 2 beds left, which were later filled by 2 Koreans.
That night we were all hanging out and the Koreans were quietly minding their own business. It was pretty hot, as Vietnam usually is, so we had the ceiling fans going strong.
Just before turning out the lights, I bent down to the lower bunk and asked if it was ok to turn them off and leave the fan on. I get a mostly blank stare as he murmured a word or two. It didn't sound likely anything close to a "no" do I smiled and said goodnight!
Fast forward to breakfast the next morning, and we're talking about our sleep and someone asks if we heard what they said before turning off the lights. Turns out it was "fan death." Most of us hadn't heard of it before.
Poor guys probably didn't sleep all night.