In To Kill a Mockingbird, why is Boo considered a mockingbird?
Arthur "Boo" Radley is considered one of the two characters in this story symbolized by the mockingbird. While Tom Robinson is the other, the reason why Boo is considered a "mockingbird" takes us back to the first part of the novel, where Atticus explains that the children are not to shoot at mockingbirds because all they do is sing. They do not molest crops, other animals, or humans. They are completely innocent, harmless birds whose sole purpose is to produce beautiful songs.
Boo is considered a "mockingbird" because he is unjustly treated despite his innocence: That is, the community perceives him as a misfit and as a criminal sort due to stories of his youth. He was alleged to have stabbed his father, Nathan, and another rumor stated that he was kept in the courthouse basement before being "chained" to his bed because of insanity. Because Boo winds up being an innocent man unjustly treated, he can be compared to the mockingbird, just as Tom Robinson is.
The title "To Kill a Mockingbird" means to kill innocence. Boo is considered a mockingbird because the entire town has labeled him as an outsider even though he has never done anything to harm anyone in the town. The townspeople claim that he stabbed his father with a pair of scissors, and whisper about him as he passes.