Believe it or not, Marked by Fire is named after Abyssinia. Say what? Check it out:
In Ponca City, in the cool of the evening, the older people invariably sat out on their porches to reiterate the events of the day. […] They were particularly interested in the new baby, Abyssinia. The women of Ponca City considered themselves midwives-in-common at her birth.
She filled their conversations.
"Remember it like it was only yesterday," one of them commented.
"Born in the cotton field."
"Came here marked, too."
"Marked by the fire!" (3.1-6)
Born in a cotton field next to a fire built by the foreman, "[a]n ember jumped out of the blaze and branded the child" (3.12), so Abyssinia is literally marked by fire. And since this book is all about her, the title is a shout-out to our leading lady in a very literal way.
There's a more subtle implication here, too, though: The fire that Trembling Sally sets to Lily Norene's house is the fire that ultimately kills Trembling Sally, ending her reign of terror over Abby's life once and for all. After this, Abby comes into her own in a new way—and insofar as it's a fire that inspires this connection with her strength, Abby's born into adulthood by fire, just as she was born into life.