From Academic Kids
The bazooka is a folk musical instrument, a primitive version of a trombone, usually with a lower but less wide range. From the mouthpiece the air chamber goes into wide lengths of pipe of sizes so that the wider diameter pipe can slide around the narrower one, lengthening or shortening the instrument to change the pitch. The bazooka was popularized in the 1930s by radio comedian Bob Burns, who may have invented the instrument some 20 years earlier. The bazooka was also played by jazz musician Noone Johnson.
During World War II, the name "bazooka", derived from the musical instrument, was applied to a new anti-tank weapon.