Once upon a time there was a very lazy man. He wanted to do nothing but sleep undisturbed all day long. In order to sleep soundly he pulled out his eyes and hung them on a tree branch. He then slept very well indeed.
One day while he was asleep a crow flew by, saw his eyes on the branch, and ate them. When the lazy man awoke, he searched and searched for his eyes, but could not find them anywhere. He was so angry that he determined to ever after suck blood whenever he could. And he does so to this day.
The Khasis call a lazy man “a leech without eyes”.