The first part of the article explains the pattern, where a nickname becomes a patronymic surname, using familiar examples. This sets up the main point, which

The first part of the article explains the pattern, where a nickname becomes a patronymic surname, using familiar examples. This sets up the main point, which is that the pattern holds so reliably that when you meet a patronymic surname you can often infer the existence of a nickname, even when it's one you don't recongize. Hence the title.