By this Aunt Alexandra means that Scout and Jem come from an old, respectable and well-established family. Aunt Alexandra seems almost obsessed with people's family background and social class. This appears quite comic in the novel as she seeks to impress these notions upon Scout who doesn't understand what she is always going on about. She wants Scout and Jem to live up to this good family reputation, and to always be polite, well-dressed and well-behaved. This sets her on a collision course with Scout who doesn't want to be polite and ladylike at all. However, as Scout grows older she is able to understand where Alexandra is coming from. Alexandra is all the more anxious for Scout and Jem to learn about their family background as it seems Atticus has little interest in teaching them about this.