According to idioms.thefreedictionary.com, the term “intestinal fortitude, “...was coined around 1915 by Dr John W. Wilce of Ohio State...as a deliberately euphemistic avoidance of the word ‘guts.’” ...... read full story
"intestinal fortitude, “...was coined around 1915 by Dr John W. Wilce of Ohio State...as a deliberately euphemistic avoidance of the word ‘guts.'"