1830, from French mythe (1818) and directly from Modern Latin mythus, from Greek mythos "speech, thought, word, discourse, conversation; story, saga, tale, myth, anything delivered by word of mouth," a word of unknown origin. Beekes finds it "quite possibly Pre-Greek."
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, imaginary or fictitious object or individual" is from 1840.
1660s, "pertaining to or characterized by myths; existing only in myth," from Late Latin mythicus "legendary," from Greek mythikos, from mythos (see myth).
early 15c., "exposition of myths, the investigation and interpretation of myths," from Late Latin mythologia, from Greek mythologia "legendary lore, a telling of mythic legends; a legend, story, tale," from mythos "myth" (a word of unknown origin; see myth) + -logia (see -logy "study"). Meaning "a body or system of myths" is recorded by 1781.
1610s, "relating to mythology; of the nature of a myth," from Late Latin mythologicus, from Greek mythologikos "pertaining to legendary lore," from mythologia (see mythology). Related: Mythologically.
c. 1600, "to make into a myth," from French mythologizer, from mythologie, from Late Latin mythologia (see mythology). From 1847 as "to render mythical." Related: Mythologized; mythologizing; mythologization.
one of the divine twins (brother of Pollux), also the name of the alpha star of Gemini, Latin, from Greek Kastor, perhaps literally "he who excels." They were sons of Tyndarus, king of Sparta (but in post-Homeric myth of Zeus in the form of a swan) and Leda.