For Augustine this passage [Gen. 17:14] meant that ‘even infants are born sinners, not by their own act but because of their origin’—their origin being the primal fatherhood of Adam. And here we see what is meant by original sin, peccatum originalis in Augustine’s Latin: sin that’s already inside us, already dwelling in us at our origin, at our very conception.
Alan Jacobs, Original Sin: A Cultural History (HarperOne, 2008), xiii.