The term "ninja" has its origins in Japan and refers to a type of warrior who was trained in various forms of martial arts, stealth tactics, and espionage. Ninjas were often hired as mercenaries or spies during feudal times in Japan, and they were known for their ability to blend into the shadows, use deception, and employ surprise attacks to achieve their goals. The word "ninja" can also refer to a member of a secret society or group of assassins who practiced similar skills and techniques. Today, the term is often used in popular culture to describe someone who is sneaky, cunning, and skilled in stealth tactics.