December 05, 2012 - Day of the Ninja - Ninjas were covert agents in feudal Japan (1185-1868) who famously dressed in uniforms that disguised their faces. Words associated with ninjas include espionage, sabotage, and assassination. One word not associated with ninjas: day. So don't be surprised if you don't spot many ninjas on Day of the Ninja. Real ninjas come out after dark.