In 1794 two British warships- HMS Fortitude and HMS JUno- with 106 guns between them- attacked the Tour de Mortella on the French island of Corsica. The 16th century round tower- built by the Genoese as a defence against Barbary pirates- had a tiny garrison and only two cannon, but managed to see off the British attack with the loss of only two men. When- a few years later- the British military were thinking about defending the coast against invasion by the French they remembered the Tour de Mortella and decided they'd like some of the same- but- as Willis pointed out- being Brits- with a high-minded contempt for all things continental- they couldn't be bothered to get the name right.
A Martello tower. This one is at Seaford.