system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Where does the term 'ninja' come from if in Japanese it's 'sasuke'? And is ninjutsu something different in Japanese? Sasukejutsu?

I was watching a documentary and it occurred to me that the Japanese-speakers weren't actually saying the word 'ninja'.
gpt
Are you talking about the show Ninja Warrior? That show was called Sasuke. Ninja is a Japanese word, as is the alternate reading, Shinobi. The word literally stems from the character "endure." 

There's arguments that there was never really a historical ninjutsu, as a distinct art, but that most of the ninja aesthetic comes from theater, where the all-black outfit originated with stagehands.