The band Flyleaf came up with their name because a Flyleaf is a blank page before and after a book. Flyleaf's connection to it is that they think of a flyleaf as a beginning and end of a life, and with there song they're giving you the story of their lives, and their problems.
The song "Cassie" was on one of the albums that Flyleaf released when they were still known as Passerby. It first came out on the Broken Wings (EP) album by Passerby. The first time it was featured by Flyleaf was on the Flyleaf (EP) album.