“Historically, the Germans had a habit of associating the names of objects with the sounds they made. After bell makers-turned-cannon-makers learned that by closing off the mouth of the cannon before lighting the fuse, the entire cannon could be made to explode, the device they invented became known as the 'bum' (for boom!). In keeping with this tradition, the first one-thousand-pound bomb was dubbed 'ein laussen bum' (meaning, "a loud boom"). After the first atomic bomb was dropped on Hiroshima, they called the fission device 'ein grossen laussen bum' (or, "a big loud boom"). The next obvious step was the fusion, or H-bomb, which was pronounced 'ein grossen laussen bum all ist kaput!”
Book:Dust