I think he just meant the “Panzer” part, which means armoured vehicle. A dragon is something armoured, like a tank since it fires at enemies.
Dragoons are heavily armed mounted troops in English. So together, “Panzer Dragoon” represents the dragon and the rider pair. That is my interpretation anyway. Dragoon sounds like dragon of course, so it has that double meaning. Like the game’s storyline, it’s probably supposed to have multiple intepretations.