Shinobi were spies for hire, not movie assassins in black
Popular myth casts ninja as stealth assassins; historical evidence for that specialty is thin. In Sengoku Japan, Iga and Kōka jizamurai formed ikki leagues and sold mercenary spying—the shinobi craft whose kanji read ninja in Chinese-style pronunciation.
Antecedents may reach the twelfth century. The word shinobi appears by the late eighth century in Man'yōshū poems; the root means to steal away or hide, hence forbearance and invisibility, while mono means person. Regional slang included monomi, nokizaru, rappa, kusa, and Iga-mono long before ninja was common.
Kunoichi as female ninja is modern fiction slang built from strokes of the woman kanji. In English the plural can stay ninja, echoing the lack of grammatical number in Japanese, or take the regular form ninjas.
Hard evidence is scarce. Tradition names Otomono Sahito, supposedly employed by Prince Shotoku (574 to 622), as the first ninja, and the title has even been pinned on the semi-legendary Yamato Takeru, who in the Kojiki disguised himself as a maiden to kill two Kumaso chiefs, though such early tales probably have nothing to do with later shinobi. The 14th-century chronicle Taiheiki credits an unnamed, highly skilled shinobi with burning a castle, and only in the 15th century were spies trained specifically for the work. By the Sengoku era shinobi served as spies, scouts, surprise attackers and agitators, organised into guilds with their own territories and a ranking system topped by the jōnin. The Iga families lived in what is now Mie Prefecture and the Kōka families near a village in present-day Shiga, and an Ashikaga record praises the Kawai family of Iga for shinobi work when the shogun Yoshihisa attacked Rokkaku Takayori.
Source: Ninja
