What does Bunk mean?

The word "bunk" is short for "bunkum," an old-fashioned way of saying "nonsense." Henry Ford, the famous car manufacturer and industrialist, coined the expression "history is bunk." What he meant by this was that we should ignore the past and look to the future. This is the perfect expression for the dystopian society in Brave New World. Ford's notorious phrase has become almost an article of faith in the setting of Brave New World as ignorance of the past—the pre-Fordian era—is imperative for the World State's continued control.
Mustapha Mond is one of the world's ten Regional Controllers; he is in charge of Western Europe. He is a dictator, referred to as "His Fordship," showing us once more how important Henry Ford's maxim is to this brave new world. For the Resident Controller it is essential that he is able to rewrite history to maintain his authority. If people are ignorant of the past, they cannot challenge the distorted vision presented to them by the state. Nor can they delve into history to find examples that will enable them to challenge the current social and political order. For the World State, control of the past is as important as control of the present and future.
In chapter 3, Mond gives a lecture in which he provides his audience with a very lurid and distorted view of pre-Fordian history, one that concentrates on war, violence, disease, and economic collapse. By giving such a heavily rewritten account of pre-Fordian existence, Mond is getting the people to accept that the Fordian world is the best possible world and that they should be immensely grateful and relieved to live in such a world without the horrors of the past.