In the 1998 Roland Emmerich-directed film Godzilla,* a Japanese sailor who survived an attack by the monster early in the film identifies the creature as "Gojira."
Later in the film, news reporter Charles Caiman (played by Harry Shearer) reports on this, where he translates that name into English as "Godzilla," and proceeds to explain [emphasis added]:
Godzilla. That's what Japanese sailors called him in song. A mythological sea dragon that filled their hearts with fear.
While I am aware that Godzilla was created in a post-WWII era Japan (having experienced a massive amount of destruction from the deployment and detonation of two nuclear bombs by the U.S.) and that the subject of nuclear weapons was incorporated into the story and the character (such as with his atomic breath), I'm curious if there is anything to suggest that the monster (or at least its name) was also based on or inspired by an older legendary or mythological creature? Or was this just a case of the writer/director taking liberty with the material for the sake of worldbuilding and creating an in-universe explanation for the origin of the name attributed by the Japanaes sailor to the monster?
*Note: I'd like to point out that I'm aware that the 1998 film is not well-regarded by fans and has been denounced by Toho (the studio that created and owns the rights to Godzilla), to the point where the film's monster is now officially known as simply "Zilla" instead of Godzilla (in reference to Toho's harsh criticism that the film "took the 'God' out of 'Godzilla'").