When Legendary studios decided to reboot the Godzilla and King Kong franchises into a shared universe, they had to find a way to keep things fresh while paying homage to both character's extensive cinematic history. Recently, director of Godzilla: King of Monsters, Michael Dougherty took to Twitter to explain why the nomenclature for their story's monsters was changed from Kaiju to MUTOs and Titans.
In the original series of Godzilla movies created by Toho studios, the monstrous lizard and its ilk are referred to as Kaiju, a Japanese word that means 'Strange Creature'. The word has since been used extensively in Asian pop culture when referring to giant animals in monster movies.
For the reboot of Godzilla, however, the monsters are initially called MUTOs, which is the acronym for Massive Unidentified Terrestrial Organisms. According to Dougherty, once the monster is classified by the government organization Monarch, it is no longer considered unidentified and thereafter known as a 'Titan'.
Just as the word 'Kaiju' draws on Japanese folklore, 'Titan' comes from Greek mythology, and is a reference to the precursors of the Greek gods, the towering race of beings which included Kronos and his family. These beings were considered primordial, unstoppable forces of nature, just like Godzilla and its ilk.
The final reason that Dougherty mentions for the name change of the monsters is a more practical one. The word 'Kaiju' had already entered popular usage in the west with the success of Guillermo Del Tero's own take on the genre, Pacific Rim. To avoid comparisons with that movie, and to avoid confusion over whether Del Toro's film is a part of the Godzilla storyline, the studio hit upon the change in nomenclature.
Back in 2017, the director of Pacific Rim: Uprising stated that there have been talks of a crossover between their franchise and the Titansverse, meaning there may yet come a time when we get to see Kong or Godzilla getting put in their place by humans operating Jaegers.
For now, however, the giant ape and the giant lizard have a personal beef to settle first. Their upcoming film will pit the two most famous giant monsters against one another in a brawl from which only one victor can emerge.
In Godzilla: King of the Monsters, the lizard proved his alpha status among the titans, and the movie ended with the rest of the monsters answering his call and bowing in supplication. Kong was noticeably absent from the scene, and the novelization of the film revealed that the giant ape had heard the call, but chooses to ignore it.
But continuing to ignore the call is no longer an option since it was revealed that Godzilla and his cohorts are making a beeline for Kong's home, Skull Island. Monarch is also building a giant mechanical contraption to deal with the threat of the titans. Now would be a perfect time for the mechanical giant to be revealed to be a Jaegar, thus kickstarting the crossover with Pacific Rim that fans have been demanding.