Brain Snacks: Tasty Tidbits of Knowledge
Briony wasn't always a Briony. Originally, Billingsley was writing a fairy story and Briony was named after a fairy. She turned out to be too prickly however, and as the story moved away from the fairy world, Briony became Briony as we know her. (Source.)
Briony's self doubt and confusion about the truth is based on a true story—Billingsley remembers feeling like that when her own mother negated the feelings she had when she was young. The author then gave Briony those insecurities she had as a child. (Source.)