Books can also have barn names. They may or may not partake of the words on the cover. In my own mind, some of mine are titled by the protagonist's name and (if part of a series) by a number: That's true of the Familias Regnant group: Heris-3 is the third book which centers on Heris Serrano. Esmay-2 is the second book in which Esmay Suiza was the co-equal or main character; Paks-3 is the last volume in the Deed. Others are related to the title: Generation Warriors is GenWar and Remnant Population goes by the barn name of RemPop. The Vatta's War books are Vatta 1 through 5. (Yes, you can yell out the door to a passing book, "Vatta-4 get in here!" Your neighbors may look at you funny, though.) The Speed of Dark has been uncooperative in the barn-name-game. Sigh.
Because I thought that Kieri Phelen would be the lead character in the new Paksworld books, I set out folders Kieri-1, Kieri-2, etc. for the files-to-be. But...it's not working out quite like that. Book one, with the title Oath of Fealty, is still in my head as Kieri-1. Book two now has a title, Kings of the North, and once that firmed up it immediately suggested Kings as its barn name.