Also, Kahnemann talked about conscious and unconscious thought, not about "gut thought" and "brain thought." You can teach yourself to behave in certain ways, to just react. That doesn't mean you have a smarter stomach than the next person!
Kahnemann's framework maps neatly onto this idea if you consider the seat of unconscious thought not to be localized in the brain (i.e. that all neurons think to some extent), and the seat of conscious thought to be in the prefrontal cortex and its tight interconnections with other brain regions via the default mode network.
Just to pursue this thread: the Online Etymology Dictionary says
> The notion of the intestines as a seat of emotions is ancient (see bowel) and probably explains expressions such as gut reaction (1963), gut feeling (by 1970), and compare guts. Gut check attested by 1976.
where "guts" says:
> The idea of the bowels as the seat of the spirit goes back to at least mid-14c. (compare bowel).
and "bowel" says:
> The transferred sense of "the viscera as the seat of emotions" is from late 14c.; especially "inner parts as the seat of pity or kindness," hence "tenderness, compassion." Greek splankhnon (from the same PIE root as spleen) was a word for the principal internal organs, which also were felt in ancient times to be the seat of various emotions. Greek poets, from Aeschylus down, regarded the bowels as the seat of the more violent passions such as anger and love, but by the Hebrews they were seen as the seat of tender affections, especially kindness, benevolence, and compassion. Splankhnon was used in Septuagint to translate a Hebrew word, and from thence early Bibles in English rendered it in its literal sense as bowels, which thus acquired in English a secondary meaning of "pity, compassion" (late 14c.). But in later editions the word often was translated as heart.