Pom poms

British pom-poms firing at kamikazes in the Pacific during WWII.

Wikipedia: "QF 2 pounder naval gun: The 2-pounder gun, officially designated the QF 2-pounder (QF denoting "quick firing") and universally known as the pom-pom, was a 40-millimetre (1.6 in) British autocannon, used famously as an anti-aircraft gun by the Royal Navy. The name came from the sound that the original models make when firing. Although these were 2-pounder guns, in that they fired a projectile with a weight of 2 pounds, they were not the same gun as that used by the British Army as an anti-tank weapon or to equip British tanks and certain armoured cars."