The Rush to Patent the Atomic Bomb : NPR: "The U.S. atomic bomb was such a secret, scientists and engineers sometimes talked in code. It was the Manhattan Project, not 'The Atomic Bomb Project.' Plutonium was referred to as 'copper,' and the bomb itself as 'the gadget.'"
But at the same time, scientists and engineers were furiously filing secret patent applications that described many of the parts in exquisite detail. Those patents sat not behind the fences at Los Alamos, but in a vault at the U.S. Patent Office.