The story
From organ + gun. The multiple barrels of the device were thought to resemble the pipes of a pipe organ.
Etymology from Wiktionary, CC BY-SA 4.0.
organ gun
or·gan gunToday it means: A large, portable firearm normally supported by wheels, in which bullets may be fired from a row of several tubes in succession; it was chiefly used from the 14th to the 17th century. Full definition →