IMHO, what I have always taken as MYTH was the Greek and Roman Myths. In my mind Myth referred to the Greek & Roman Mythology of yore.
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Difference Between Myths, Legends, And Fables
Myths, Fables, Legends, and Fairy Tales are all considered types of stories. Though they are all types of stories, they have some key differences. A myth is a traditional story that is used to explain a belief or perspective of the world. They are often used to provide a reason for the way the world is, such as the myths about the Greek gods. Each was a god of a particular part of nature or idea. They were said to be the reason that part of nature existed. A legend is a story that has been passed down through generations via oral storytelling. They are usually stories about real people, places, and events of the past. The facts within these stories are known to be somewhat exaggerated. A fable’s overall purpose is to teach a lesson or a moral using characters that cannot talk in real life (such as animals, plants, and forces of nature). Fairy tales are stories for children that often include a magical or supernatural element, such as elves, witches, or special animals. These stories most often begin with the phrase Once upon a time
Myths- are stories that are passed down about how or why something came to be.
Legends- are designed to teach a lesson about a real person in History, with a few facts dramatically changed.
Fables- are stories that are passed down, with a good lesson to be learned, and are about animals, plants, or forces of nature that are humanlike.
Fairy tales- are stories that are specifically for kids, involve magical characters, have good and evil characters, and generally start with “once upon a time.”
https://www.mometrix.com/academy/myth-legend-and-tall-tale/
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myth (n.)
1830, from French Mythe (1818) and directly from Modern Latin mythus, from Greek mythos"speech, thought, story, myth, anything delivered by word of mouth," of unknown origin.
Myths are "stories about divine beings, generally arranged in a coherent system; they are revered as true and sacred; they are endorsed by rulers and priests; and closely linked to religion. Once this link is broken, and the actors in the story are not regarded as gods but as human heroes, giants or fairies, it is no longer a myth but a folktale. Where the central actor is divine but the story is trivial ... the result is religious legend, not myth." [J. Simpson & S. Roud, "Dictionary of English Folklore," Oxford, 2000, p.254]
General sense of "untrue story, rumor" is from 1840.
https://www.etymonline.com/word/myth
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IMO it is a borrowed colloquialism. We are describing something as "Mythological" as an adjective.
And because it is a "Western European" word I relate the word myth to the Roman and Greek [where Greece had democracy and Rome had a supreme Fascist with a senate.]
