Oppenheimer spoke these words in the television documentary The Decision to Drop the Bomb (1965). In the literature, the quote normally appears in the form shatterer of worlds, because this was the form in which it first appeared in print, in Time magazine on November 8, 1948. It later appeared in Robert Jungk's Brighter than a Thousand Suns: A Personal History of the Atomic Scientists (1958), which was based on an interview with Oppenheimer
IMO, it's possible atomic/nuclear weapons had been used on Earth in ancient times. we may have lost that knowledge, yet memory of it still rings in tales, fables, and myths...