“What is the difference between butterfly and spud?”, “What is the difference between eye and light?”, “What is the difference between pill and pell?”

The difference between butterfly and spud is that butterfly is to cut almost entirely in half and spread the halves apart, in a shape suggesting the wings of a butterfly while spud is (drilling) to begin to drill an oil well; to drill by moving the drill bit and shaft up and down, or by raising and dropping a bit.