Why The Atom Bombs Dropped On Japan Were Named ‘Little Boy’ And ‘Fat Man’
“Little Boy” used uranium-235 and had a slim, 10-foot structure—long like a car but narrow and “cute.” In contrast, “Fat Man” was much bulkier, with a heavier, plutonium-based design.
On August 6, 1945, during the Second World War, the first atomic bomb was dropped on Hiroshima. Two days later, another bomb was dropped on Nagasaki, leading to widespread destruction. Thousands lost their lives, homes were flattened, and everything was left charred. The two nuclear bombs used by the United States were named “Little Boy” and “Fat Man.” The names have intrigued many people over time.
The Name And Its Significance
“Little Boy” was a uranium-235 bomb, with a relatively straightforward and slim design. It was about 10 feet in length and 28 inches in diameter—similar in length to a car, but extremely narrow. It was considered small and “cute” when compared to other bomb types. On the other hand, “Fat Man” was broader and significantly heavier.
This bomb, made using plutonium-239, had a more complex and heavier structure than “Little Boy.” It had a rounded, wider shape, measuring about 5 feet in diameter and 10.6 feet in length, and weighed nearly 10,300 pounds.
The Practice of Codenaming
Weapons under the Manhattan Project were often given codenames to maintain secrecy. Names like “Little Boy” and “Fat Man” were deliberately non-technical, informal, and easy to remember. They were mainly used for everyday communication among the scientists, rather than for any deep military or philosophical significance.
Some historians believe “Little Boy” may have been influenced by characters from popular culture or humour of the 1940s, such as those from films like The Thin Man (1942).
Were The Names Intended As Jokes?
Scientists involved in the Manhattan Project, including Robert Oppenheimer and his team, often used humour as a way to ease the pressure of their high-stress work. The bomb names reflected this light-hearted approach. It’s likely that these names weren’t symbolic, but simply practical, humorous codenames—a common trend among scientists of the time.
Some historical accounts credit Robert Serber, a physicist and close associate of Oppenheimer, with choosing the bomb names.
Names For Other Bombs And Tests
The United States continued naming other bombs in unique ways. Variants of the “Fat Man” design were known as “Roundfish” and “Helda.” Meanwhile, the Soviet Union gave its most powerful bomb the name Tsar Bomba, echoing the Russian tradition of Tsars.
Do All Bombs Have Names?
Atomic weapons developed during the Second World War were given distinct names based on their design or project. In modern times, nuclear weapons are typically referred to using codenames or model numbers (e.g., B61, W88, AGM-114 Hellfire), which are more technical or military in nature, rather than personal or humorous. Examples include the B61, a US nuclear bomb with several variants, and the GBU-43/B—nicknamed MOAB, the “Mother of All Bombs”—a powerful non-nuclear weapon known for its sheer destructive power.
Did The US Make Only Two Atomic Bombs?
The US had prepared the two atomic bombs that were dropped on Japan in 1945, with the initial plan focused on using just these two. However, historical records show that a third bomb was not immediately available at the time, though the Manhattan Project had begun producing more.
Plutonium cores for additional bombs were being developed at Los Alamos Laboratory, and it was estimated that another bomb could be ready by late August 1945—around August 19. The US Army had considered using more bombs if Japan didn’t surrender after the first two attacks. Some documents reveal that additional bombs could have been ready by September or October 1945 for deployment on other Japanese cities or strategic targets.
