Final answer:
The quote is attributed to Martin Luther, illustrating his wit during an episode of constipation and providing a humanizing glimpse into the life of a historical figure.
Step-by-step explanation:
The quote "he had 'excreted everything but his brains' then moments later said 'there they go, there they go'" is famously attributed to Martin Luther, the German professor of theology who is widely known for his influence on Protestant Reformation. Luther reportedly made this statement while suffering from constipation, displaying his characteristic sharp wit even during personal discomfort. Although this incident reflects Luther's humor, it also underscores the humanizing aspects of historical figures that endure physical ailments just like any other person.