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.

1801, "a story of a house," from Scottish flat "floor or story of a house," from Old English flett "a dwelling, hall; floor, ground," from Proto-Germanic *flatja-, from suffixed form of PIE root *plat- "to spread." Meaning "floor or part of a floor set up as an apartment" is from 1824. Directly from flat (adj.) come the senses "level ground near water" (late 13c.); "a flat surface, the flat part of anything" (1374), and "low shoe" (1834).

"impudent, presumptuous," 1859 (1850 as the nickname of a misbehaving boy in a story), from cheek in its sense of "insolence" + -y (2). Related: Cheekily; cheekiness (1841). 

early 15c., narracioun, "act of telling a story or recounting in order the particulars of some action, occurrence, or affair," also "that which is narrated or recounted, a story, an account of events," from Old French narracion "account, statement, a relating, recounting, narrating, narrative tale," and directly from Latin narrationem (nominative narratio) "a relating, narrative," noun of action from past-participle stem of narrare "to tell, relate, recount, explain," literally "to make acquainted with," from gnarus "knowing," from PIE *gne-ro-, suffixed form of root *gno- "to know."

"a short novel or long short-story," 1901, from Italian; see novel (n.).

It is not quite so clear as to when and where a piece of fiction ceases to be a novella and becomes a novel. The frontiers are so vague that one is obliged to recognize a middle species, or rather a middle magnitude, which paradoxically, but necessarily enough, we call the novelette. [W.D. Howells, "Some Anomalies of the Short Story," The North American Review, vol. CLXXIII, August, 1901]