"Maxim automatic gun," 1899, of imitative origin, soldiers' slang from the Boer War. For the ornamental tuft, see pompom.
Entries linking to pom-pom
pompom n.
"ornamental round tuft" (originally on a hat, etc.), 1897, an alteration of pompon "ornamental tuft; tuft-like flower head" (1748, pong-pong), from French pompon (1725), a word of unknown origin; perhaps related to Old French pompe "pomp."