The rubber treat commonnly given to young babies to suck is decribed by Americans as a pacifier, where New Zealanders retain the British term dummy. In New Zealand & Australia the expression to spit the dummy has evolved as a way of deccribing someone who has finally had enough of restrictions or is at loggerheads with some authority and eventuually breaks out against them.. But everyone knows that when a real baby spits out a real dummy its because they intend to make a strident and unwelcome noise.