I was always under the impression that he lifted the title from a huge beast of an aero-engined racing car driven in the 1920s at Brooklands by the eccentric millionaire Count Louis Zborowski, which was known as "Chitty-Bang-Bang" from the noise it made when under way.
Gadget-laden cars, improbably named women and fiendish villains; typical Fleming territory if you ask me!
Plus Gert Frobe (Goldfinger) is in the movie.