The book's title is the translation of the Hmong phrase for epilepsy. But it's a lot more than just naming the book Epilepsy—that phrase, and the cultural baggage connected to it, speaks volumes about this book's major themes.
So let's get down to it. In America, epilepsy is seen as a disease. As such, doctors like Peggy and Neil make it their mission to rid Lia Lee of the condition, even when her parents have concerns about the method of treatment.
In Hmong culture, however, epilepsy is known as qaug dab peg, which is translated as "the spirit catches you and you fall down" (that's right, the title). In contrast to the Western view, the condition is actually considered a blessing—many shamans, known as txiv neeb, use their seizures to take "journeys into the realm of the unseen" (3.3). Sounds a lot cooler when you put it like that.
It's pretty clear that there's not a ton of middle ground between these two viewpoints. The resulting tension reflects a larger cultural conflict between the American and Hmong cultures—and that is exactly what our author Anne Fadiman is trying to illuminate. Pretty all-encompassing, then, as far as titles go.