ClioyoudaoicibaDictYouDict
"muse of history, muse who sings of glorious actions," usually represented with a scroll and manuscript case, from Latin Clio, from Greek Kleio, literally "the proclaimer," from kleiein "to tell of, celebrate, make famous," from kleos "rumor, report, news; good report, fame, glory," from PIE *klew-yo-, from root *kleu- "to hear" (see listen). Related to the -kles in Damocles, etc.
marathon (n.)youdaoicibaDictYouDict
1896, marathon race, from story of Greek hero Pheidippides, who in 490 B.C.E. ran the 26 miles and 385 yards to Athens from the Plains of Marathon to tell of the allied Greek victory there over Persian army. The original story (Herodotus) is that he ran from Athens to Sparta to seek aid, which arrived too late to participate in the battle. Introduced as an athletic event in the 1896 revival of the Olympic Games, based on a later, less likely story, and quickly extended to mean "any very long event or activity." The place name is literally "fennel-field." Related: Marathoner (by 1912).
troll (n.1)youdaoicibaDictYouDict
supernatural being in Scandinavian mythology and folklore, 1610s (with an isolated use mid-14c.), from Old Norse troll "giant being not of the human race, evil spirit, monster." Some speculate that it originally meant "creature that walks clumsily," and derives from Proto-Germanic *truzlan, from *truzlanan (see troll (v.)). But it seems to have been a general supernatural word, such as Swedish trolla "to charm, bewitch;" Old Norse trolldomr "witchcraft."

The old sagas tell of the troll-bull, a supernatural being in the form of a bull, as well as boar-trolls. There were troll-maidens, troll-wives, and troll-women; the trollman, a magician or wizard, and the troll-drum, used in Lappish magic rites. The word was popularized in literary English by 19c. antiquarians, but it has been current in the Shetlands and Orkneys since Viking times. The first record of the word in modern English is from a court document from the Shetlands, regarding a certain Catherine, who, among other things, was accused of "airt and pairt of witchcraft and sorcerie, in hanting and seeing the Trollis ryse out of the kyrk yeard of Hildiswick."

Originally conceived as a race of malevolent giants, they have suffered the same fate as the Celtic Danann and by 19c. were regarded by peasants in in Denmark and Sweden as dwarfs and imps supposed to live in caves or under the ground.
They are obliging and neighbourly; freely lending and borrowing, and elsewise keeping up a friendly intercourse with mankind. But they have a sad propensity to thieving, not only stealing provisions, but even women and children. [Thomas Keightley, "The Fairy Mythology," London, 1850]