Carrot and stick (also "carrot or stick") is an idiom
that refers to a policy of offering a combination of rewards and
punishment to induce behavior. Some claim that this usage of phrase is
erroneous, and that in fact comes from the figure of a carrot on a stick.
In this case, the driver would tie a carrot on a string to a long stick
and dangle it in front of the donkey, just out of its reach. As the
donkey moved forward to get the carrot, it pulled the cart and the
driver so that the carrot would always remain out of reach.
