The evening was dragging on as his host regaled Nasruddin with stories in which Nasruddin had no interest.
Finally, Nasruddin could not help himself: he yawned.
This prompted his host to change the topic. "You are a learned man, Nasruddin," he said. "Why is it that people yawn?"
"It's either from lack of sleep or lack of food," declared Nasruddin. "And I got a very good night's sleep last night!"
Inspired by: Mulla's Donkey and Other Friends by Mehdi Nakosteen
Notes: This story is on p. 117 of the book.