Foi o título provisório do filme baseado no nome de sua filha:
Nolan’s father died in 2009, after a year-long battle with cancer that was diagnosed just as the film-maker was finishing Inception, and as Jonah was starting to write Interstellar. His father’s diagnosis was “very much in my mind,” Jonah said, “the connection that you have with your parents. It was the background to much of it.” Nolan himself sees Interstellar more in terms of his relationship with his own children – Rory, Magnus, Oliver and Flora – all of whom have given him the working titles for the last four of his movies. The Dark Knight was “Rory’s First Kiss”, Inception was “Oliver’s Arrow”, The Dark Knight Rises was “Magnus Rex”, and Interstellar was “Flora’s Letter”
Fonte: theguardian.com