Fire in the belly

Working on a lyrical annotation project and this phrase comes up... I'm guessing it stems either from the days of coal-driven boats/locomotives, or from a firewater/alcohol reference, but I haven't found any substantiation either way. Any help?

--Dave

It was the title of a book on men by Sam Keen; it referred, I think, to driving passions, "gut feelings." The link below goes to more info

[Dead link - removed]