What is the origin of the phrase 'to cry wolf'?

Answer 1

It originates from a morality tale literally called "The Boy Who Cried Wolf". The story is about a Sheppard boy who is told to watch watch his villages flock of sheep and protect them against wolves. He's given a horn to call the villagers to attack the wolf if it showed up, eventually the boy got bored and blows the horn to call out the villagers. He did this again a few days later. After this the villagers stop responding to the horn, so when the wolf did show up, the villagers ignored the horn and the wolf killed several sheep.

Answer 2

It comes from the old fable by Aesop called "The Sheppard Boy and the Wolf", or "The Boy Who Cried Wolf".

In the story the boy, to amuse himself, would call for help, claiming the wolf was attacking his flock of sheep. When the villagers would come to his aid they would see no wolf and be angry. After a couple of times doing this, the villagers ignored the boy. Unfortunately, when the wolf DID attack and the boy called for help, nobody came to his aid.

Hence, to cry wolf is to falsely call for help.