My insight tells me that the saying has its "punch" in contrasting what the biting party might expect: "that once bitten => once shy". But the point is to correct his expectation kind of saying "no Siree ... it'sI am not taking it lightly, I am taking it twice as seriously as you would expect. It's not a one-to-one relation"relationship". (If it was one-to-one the biter could set into motion a circularly-recurring-cyclical-cycle c=2rPI :)