Running Dog is a literal translation into English of the Chinese/Korean/Communist insult 走狗 'Zou Gou', meaning lackey. Its first recorded use in English was in 1937.
Running Dog is also the title of a 1978 novel by Don DeLillo. At its center is a rumored pornographic film of Adolf Hitler, purportedly filmed in his bunker in the climactic days of Berlin's fall. The novel follows a journalist as she tries to penetrate a murky black market of wealthy erotic-art collectors in order to locate the film. The tale grows increasingly wild and violent as she closes in on this bizarre grail.