Hello Spiral, Ninja were originally called Shinobi-no-jutsu amongst other names. Ninja today often associate the word "budo" with their art, but this is incorrect. It is a bugei/bujutsu art. There were "ninja like" activities before ninjutsu became formalised such as Prince Yamoto, etc but the true concepts of ninjutsu originate from China many years before they were "officially" used in Japan. Ninjas do come from Japan, but their "concepts" originate from China. There were 2 types of ninja, the most common were Samurai of a particular clan who were trained in Shinobi ways. Then there were the type of Ninja you could hire from Iga province who were used by Daimyo for jobs they did not want to be associated with. The great Don F Draegar who had the most knowledge of any westerner in the ways of the warrior arts of Japan, reckoned that no genuine ninja could be taller than 5'3", this was after he was taken to a genuine ninjutsu training compound.