Note: Tracking the origins for the majority of popular sayings isn't easy, in fact, it's often impossible. Usually what you will find are plausible theories that try to explain a phrase's origin, but remember, they are just theories.
The quotes on this website come from older books, poems, newspapers, etc. They can be used as an indicator to determine how old some of these sayings are. Keep in mind, however, that if a saying is being used in an old newspaper, it's probably already well-known, so it's likely older than that.
knowyourphrase.com - Common Phrases and Idioms - Meanings and Origins
The origins for this phrase are believed to be from Aesop, a Greek fabulist who is said to have lived from 620 to 560 BCE. He wrote a number of different fables known collectively as Aesop's Fables.
One of the stories credited to his name tells of a young boy who was given the responsibility of watching over some sheep for the night. The boy eventually grew bored with his assignment and thought it would be rather humorous if he pretended to be in danger, so he started shouting "wolf, wolf!" His plan worked, as the people nearby heard his cries for help and came rushing to lend their support, only to learn that it was all a silly ruse.
After this repeated a few more times, the people wisened up and no longer responded to the boy's deceitful cries. Later on, a real wolf shows up and the boy now seriously starts crying for help, but it's too late, because nobody would listen to him any longer.
Indeed, when you constantly lie, you lose the trust of others. Thus, the phrase 'crying wolf' is thought to have originated from this story; it references the lying boy.
* This is the third time my wife has complained of a mouse running around and I thought she was crying wolf, but when I ran into the small rodent in the kitchen, I realized I was wrong.
* We heard someone screaming for help nearby and decided to investigate what was wrong, but we soon learned everything was okay and that it was just some woman crying wolf.