The Emperor, at least during the time Cos Dashit ruled the Empire, was identified as "Your Highness." In addition, a common phrase for the Emperor when celebrating a speech was "Long Live the Emperor!"
This incarnation of the Emperor first appeared in the 1974 rough draft of Star Wars. In this story treatment, the Emperor had been a position used since at least 100,000 years prior to the events of the story and was originally benevolent. This was changed by the final draft to the Galactic Emperor as being a position adopted after the Galactic Republic was reformatted into the Galactic Empire, although hints of its original conception were retained in the novelization for A New Hope, including Obi-Wan Kenobi's mention of there being multiple Emperors, with the later ones becoming corrupt overtime with the prior Emperor being assassinated. Similarly, the same novelization also stated that Palpatine was a puppet ruler.
However, in 2013, a comic book adaptation of George Lucas' rough draft by Dark Horse Comics, titled The Star Wars was announced.