What is "linin"? Why do people in Calpurnia's church use it?
Why does Calp. speak the dialect of the "colored folks"when she is in her church?
The answer to this question can be found in chapter 12 of To Kill a Mockingbird. When Calpurnia takes Jem and Scout to the First Purchase Church, they are perplexed when the congregation rises to sing hymns. "How're we gonna sing it if there ain't no hymn books," Scout asks Calpurnia. The way that the congregation sings is different than their own church. Zeebo, the music superintendent, sings a hymn one line at a time from a hymnal, and the congregation repeats that line back to him. Scout is struck by the fact that they are all "on pitch" and moved by how the hymn ends in a "melancholy murmur." This, Calpurnia reveals, is called "linin.' " She says they use the technique because only about four people in the congregation, including her, can read. As for Calpurnia's changes in dialect, she tells the children that people would think she was "puttin' on airs" if she spoke otherwise at church. She believes that putting on airs would not change the speech of her fellow churchgoers (something both children seem to think would be appropriate) and in fact would offend them. So, she explains that she talks in ways that are appropriate to each of the two worlds she inhabits. This demonstrates the cultural chasm that exists along racial lines in Maycomb. The children are very close to Calpurnia, but they cannot fully know her. Scout asks if she can visit Calpurnia in her own world, demonstrating a desire to bridge that gap.
The "linin'" is what the people at the First Purchase Church do instead of having hymn books. They have to do it that way because they are too poor to have the books and besides, they can't all read. So the leader gives one line from the hymn and they all sing it. Then he gives the next.
If Calpurnia went to the black church and started talking like a white person, everyone would accuse her of trying to act like she was better than the other black people. They would say she was trying to act white.
Calpurnia lives in two worlds, a white world and a black world. She is well aware that she is expected to behave and present a certain way when she is among each group and those behaviors and speech are very different.
Calpurnia is a unique individual but very much like many women of her day. She has spent her life taking care of white people and their children and homes. Yet, it is clear that she respects Atticus and feels fortunate to be able to work for someone who respects her color and does not degrade the black people.
When she takes the children to the church it ais an awakening for them because they have the opportunity to learn tha dialects are cultural and in the south, at the time, race related. In many ways Calpurnia demonstrates her high level of intelligence by showing and explaining to the children the difference between the ways one must present ones self.