The tale is one of Aesop's Fables and concerns a shepherd boy who repeatedly tricks nearby villagers into thinking a wolf is attacking his flock of sheep. When a wolf actually does appear and the boy again calls for help, the villagers believe that it is another false alarm and the sheep are eaten by the wolf.
Aesop may or may not have been an actual person (he probably was) who lived around 620 to 564 BCE (he probably did). His life is almost a fairy tale of its own, with branches and fabrications shared and spread throughout the years. Storytelling at that time was largely an oral tradition and storytellers and fabulists often changed tales to suit their needs with little crediting of the origins of stories.
Since Aesop was considered one of the greatest storytellers of his age, this story is one of many credited to him even though it didn't really become widespread until the 1400's after being translated into Latin and appearing in European collections of folktales.
In fact, there was no original title for this story, some calling it "Of the Child Which Kept the Sheep", "The Boy Who Lied" or my favorite, "A Boy and False Alarms".
Interestingly, while parents and educators have often used the story of "The Boy Who Cried Wolf" as a cautionary tale about the power of telling the truth, educational experiments in the last few decades have shown that reading the story actually increases a child's likelihood of lying.
But don't worry, reading "George and the Cherry Tree" has been shown to increase the likelihood of children telling the truth.
SPOILER ALERT: In the original Aesop's fable all of the sheep die in the end.
LATER ENGLISH-LANGUAGE SPOILER ALERT: The wolf also eats the boy.
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