The original Gatling gun was invented by Richard Jordan Gatling and first used in the American Civil War. Though not automatic in operation, it was a direct ancestor of today's machine guns. Gatling-style rotating barrels are still used in modern heavy machine guns such as the M61 Vulcan, the GAU-8, and the M134 Minigun, typically to increase the sheer volume of firepower while reducing the wear of each individual barrel for continued usage.
On AIBooru, gatling gun refers to any kind of heavy machine gun with multiple rotating barrels, not just the original Civil War-era Gatling gun. If the said gatling gun were small enough to be carried by a person, then the tag minigun is applicable.
