"Klaatu barada nikto" is a phrase originating in the 1951 science fiction film
The humanoid alien protagonist of the film, Klaatu (Michael Rennie), commanded Helen Benson (Patricia Neal) that, were anything to happen to him she must say the phrase to the robot Gort (Lockard Martin). In response Gort relented from destroying the Earth and resurrected Klaatu from death.
Usage in 2008 remake Edmund H. North, who wrote The Day the Earth Stood Still, also created the alien language used in the film, including the phrase "Klaatu barada nikto". The official spelling for the phrase comes directly from the script (as shown in the above image) and provides insight as to its proper pronunciation.
The phrase was never translated in the film and neither Edmund North nor 20th Century Fox ever released an official translation.
Toward the end of the film, Klaatu is pursued by the American military and orders Helen Benson to memorize the phrase, saying "There's no limit to what he [Gort] can do. He could destroy the Earth... If anything should happen to me you must go to Gort, you must say these words, 'Klaatu barada nikto', please repeat that.".
Shortly after, Klaatu is shot and killed; and Gort, knowing he has died, dissolves the polymer cube that encases him, and disintegrates the two guards standing watch. Helen Benson watches this but conveys Klaatu's message. Gort then takes her inside the spaceship and retrieves Klaatu's lifeless body, which he revives.
In the 2008 remake of The Day the Earth Stood Still, this line was added at Keanu Reeves' insistence; wherefore Klaatu uses it near the beginning of the movie to shut down Gort, and again (highly distorted and barely audible) at the end when he stops the destruction of the Earth. Although the line is not in the English subtitles, it can be heard.
Because there is no official translation of the phrase, a few notable attempts have been made to determine the phrase's meaning:
Philosophy professor Aeon J. Skoble speculates the famous phrase is part of a fail-safe feature used during diplomatic missions, whereby Gort's deadly force can be deactivated in the event the robot is undesirably triggered into a defensive posture. Skoble observes that the theme has evolved into a "staple of science fiction that the machines charged with protecting us from ourselves will misuse or abuse their power." In this interpretation the phrase apparently tells Gort that Klaatu considers escalation unnecessary.
Fantastic Films magazine explored the meaning of "Klaatu barada nikto" in a 1978 article titled The Language of Klaatu. The article, written by Tauna Le Marbe, who is listed as their "Alien Linguistics Editor," attempts to translate all the alien words Klaatu used throughout the film. In the article, the literal translation was "Stop Barbarism (I have) death, bind" and the free translation was "I die, repair me, do not retaliate."
The documentary Decoding "Klaatu Barada Nikto": Science Fiction as Metaphor examined the phrase "Klaatu barada nikto" with some of the people involved with The Day the Earth Stood Still. Robert Wise, director of the film, related a story he had with Edmund North saying North told him, "Well, it's just something I kind of cooked up. I thought it sounded good."
Billy Gray, who played Bobby Benson in the film, said that "barada nikto must mean... save earth". Florence Blaustein, widow of the producer Julian Blaustein, said North had to pass a street called Baroda every day going to work and said, "I think that's how that was born." Film historian Steven Jay Rubin, recalled an interview he had with North when he asked the question, "What is the direct translation of Klaatu barada nikto, and Edmund North said to me 'There's hope for earth, if the scientists can be reached.'"