Mitchell the author first titled the book, "Tomorrow is Another Day", from the last line. Some of the other titles included: Bugles Sang True, Not in Our Stars and Tote the Weary Load. The title Mitchell finally chose is from the first line of the third stanza of the poem, "Non Sum Qualis Eram Bonae sub Regno Cynarae" by Ernest Dowson:
I have forgot much, Cynara! gone with the wind, Flung roses, roses riotously with the throng, Dancing, to put thy pale, lost lilies out of mind...
Scarlett O'Hara uses the title phrase when she asks if "Tara" is still standing or is it "gone with the wind" which had swept through Georgia."
The title is a metaphor for the way of life that existed in the South prior to the Civil War. When taken in the context of Dowson's poem about "Cynara", the phrase "gone with the wind" is about someone who has lost his passionate feelings for his "old passion", Cynara.
Video: First of 5: Making of "Gone With The Wind" .