A Louisiana-born friend of mine tells the story his father told him:
Seems there was a young woman in the small LA town of my friend's birth who in the 1930s found that she was pregnant and unmarried. The church, concerned about her spiritual well-being suggested that if she were going to act un-church-like, perhaps she shouldn't be considering herself a member of their congregation. She repented and they kept her in the fold on her promise that she would "do better" in the future.
A few years later and still unmarried she had twins . . . the town dubbed them the "do better" girls.