In 1959, Walter C. Gregory of North Carolina State College introduced "atomic" peanuts to the world. Despite the name, they weren't radioactive peanuts.
He had exposed peanut seeds to huge amounts of radiation to create mutant strains. Then he had selected the mutant strains with the qualities (size) he liked. And in this way created jumbo-sized peanuts.
As this article at Atlas Obscura
notes, what Gregory was doing was "mutation breeding," and it's the way many of the varieties of fruit and veggies we eat nowadays are created. We no longer call it "atomic" food, though it is.
Since the 1950s and 60s, mutation breeding has created around 3,000 commercially available varieties of plant—durum wheat, rice, soybeans, barley, chickpeas, white beans, peaches, bananas, papayas, tomatoes, sunflowers, and more. Almost any grapefruit you've bought was probably a mutant.
Man and woman eating "atomic" peanuts
Kansas City Times - Jan 12, 1959