It is false that an aphorism is a cleverly worded statement that is meant to trick the listener into believing a lie.
In fact, an aphorism is an expression of general truth.
Harper Lee provides a vivid description of life in Maycomb, which is ruled by a strict system of social cues and hierarchy. There is a clear division between those who "belong" to the town, and the "others," which are clearly undesirable to the rest of the population, even when not stated out in the open.
The less desirable people all have traits that do not match the stereotype of a perfect Southern citizen. One way in which this is expressed, perhaps the most relevant one, is racial prejudice. Black people are "others," as they are considered inferior to the rest of the population.
Another example is that of the Radley family. Due to Boo Radley's mental situation, the family is shunned and their interactions with others are very restricted. Gossip and superstition play a big part in their lives, as people exchange stories about the fate of Boo Radley, and he becomes something of an urban legend.
Other stereotypes are also present, such as the idea of black men always going after white women. This stereotype causes an irrational fear among the population which makes it impossible to conduct a fair trial.
Frequently, as it modifies the sentence
It will be the second one I did that last year
