Here's why:
* Mockingbirds don't harm anything: They only sing beautiful songs, mimicking the sounds of other birds and nature. This symbolizes innocence and harmlessness.
* Mockingbirds are vulnerable: They are easily killed and have no defense against predators. This reflects the vulnerability of innocent people, especially children, in a cruel and unjust world.
* Mockingbirds represent those who are persecuted: In the novel, Tom Robinson, a black man falsely accused of rape, is compared to a mockingbird. He is unjustly punished for a crime he didn't commit, just like the mockingbird is killed for no reason.
However, the term "mockingbird" is not exclusively used for the novel. It can be used metaphorically to refer to anyone who:
* Is innocent and harmless.
* Is persecuted or unfairly treated.
* Spreads joy and beauty into the world.
So, while the specific characters associated with the "mockingbird" symbol depend on the context, the general idea remains the same: it's someone who is good, vulnerable, and deserves protection.