Connection between Interstellar and 'Flora's Letter'?

I work in a cinema, and today we received our copy of Christopher Nolan's Interstellar: which came packaged and labelled as "Flora's Letter"

As is quite well known, film's are distributed (and sometimes produced) under working titles or false titles, in order to interfere with potential pirates or thieves.

What is less well known, is that most film producers cannot resist the opportunity to leave clever clues and hints; almost like serial killers!

Even previous Nolan films have a precedent for this, being distributed as Backbreaker (The Dark Knight Rises) and Be Kind, Rewind (Memento)...

Which leads me to ask... What is the significance of 'Flora's Letter'?

Best Answer

It was the working title of the film based on his daughters name:

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”

Source: theguardian.com