At first glance, Savvy is pretty easy to understand as a title. After all, it refers directly to the magical power that each of the Beaumonts get when they turn thirteen, and this is a book about Mibs turning thirteen. Simple, right? Kind of.
If you dig a little deeper, though, and think about what savvy means outside the world of the book, you'll recognize that it also refers to "shrewdness and practical knowledge." And while this book is definitely about magical savvies, it's also about understanding the world and how to navigate it better. In other words, the Beaumont kids have to become savvy with their savvies… and all the non-magical folks have to become a bit savvier too.