A college student was tired of over thinking multiple choice test questions and said this malaphor. It is a nice mashup of “first impression” (opinion formed on first meeting someone) and “gut feeling” (an instinct or intuition about something). Both expressions involve immediate reactions to something, and are visceral in nature. Of course, a tight belt forms a first and second gut as well. A big thanks to John Kooser who heard this one and passed it on.