The story of The Shepherd's Boy and the Wolf is an Allegory said to be written by Aesop.
The story goes by (at least) one other different name and has different variations. Another name this goes by is: The Boy Who Cried Wolf.
An English Language version of the story is as follows...
A Shepherd-boy, who watched a flock of Sheep near a villiage, brought out the villagers three or four times by crying out, "Wolf! Wolf!" and when his neighbors came to help him, laughed at them for their pains. The Wolf, however, did truly come at last. The shepherd-boy, now really alarmed, shouted in an agony of terror: "Pray, do come and help me; the wolf is killing the sheep"; but no one paid any heed to his cries, nor rendered any assistance. the wolf, having no cause of fear, at his leisure lacerated or destroyed the whole flock.
The version of this story that I heard when I was a child was different than this. It went something like...
There once was a shepherd boy who was bored as he sat on the hillside watching the village sheep. To amuse himself he took a great breath and sang out, "Wolf! Wolf! The Wolf is chasing the sheep!"
The villagers came running up the hill to help the boy drive the wolf away. But when they arrived at the top of the hill, they found no wolf. The boy laughed at the sight of their angry faces.
"Don't cry 'wolf', shepherd boy," said the villagers, "when there's no wolf!" They went grumbling back down the hill.
Later, the boy sang out again, "Wolf! Wolf! The wolf is chasing the sheep!" To his naughty delight, he watched the villagers run up the hill to help him drive the wolf away.
When the villagers saw no wolf they sternly said, "Save your frightened song for when there is really something wrong! Don't cry 'wolf' when there is NO wolf!"
But the boy just grinned and watched them go grumbling down the hill once more.
Later, he saw a REAL wolf prowling about his flock. Alarmed, he leaped to his feet and sang out as loudly as he could, "Wolf! Wolf!"
But the villagers thought he was trying to fool them again, and so they didn't come.
At sunset, everyone wondered why the shepherd boy hadn't returned to the village with their sheep. They went up the hill to find the boy. They found him weeping.
"There really was a wolf here! The flock has scattered! I cried out, "Wolf!" Why didn't you come?"
An old man tried to comfort the boy as they walked back to the village.
"We'll help you look for the lost sheep in the morning," he said, putting his arm around the youth, "Nobody believes a liar...even when he is telling the truth!"
In some versions of this story, the boy is eaten by the Wolf, and the wolf eats the sheep.
The elegance of allegories, like this one, is that they are able to communicate an abstract concept in a way that is not as susceptible to corruption and redefinition as words are.
The meaning I get from this story is why you shouldn't lie. The reason is, that some day you might need others to believe what you say.
I've seen others state the meaning of this as....
There is no believing a liar, even when he speaks the truth..
At a certain (very young) age I decided I wasn't going to lie. I.e., that whenever I uttered a statement, that it would be what I believed was the truth.
I can't remember where I got this from, but I vaguely remember a story, or something, about a person who people greatly trusted. They would believe anything he said, just because HE said it. They would let him borrow their most precious possesions, just on him saying that he would return it, just because HE said it.
The man even went to a store once to buy some food. But when he went to pay for the food he discovered that he forgot his money at home. The shop keeper, knowing how trust worthy he was, told him, take the food and pay me the next time you come in here.
These people would trust him so much because from experience they knew that he didn't lie and he always kept his word. They knew if he made a statement, that he believed that it was true. They knew if he said he would do something, that he would do his best to actually do it.
I wanted people to treat me this way as well, so I decided #1 to never lie and #2 to always keep my word.
(Note, this allegory has nothing to do with keeping your word. It's just about not saying things that you know are false.)