marathon (n.)

1896, marathon race, from story of Greek hero Pheidippides, who in 490 B.C.E. ran 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.

It was introduced as an athletic event in the 1896 revival of the Olympic Games, based on a later, less likely story, that Pheidippides ran to Athens from the battlefield with news of the victory. The word quickly was extended to mean "any very long event or activity." The place name is literally "fennel-field." Related: Marathoner (by 1912); Marathonian.

Others are reading

Definitions of marathon
marathon (n.)
any long and arduous undertaking;
Synonyms: endurance contest
marathon (n.)
a footrace of 26 miles 385 yards;
Marathon (n.)
a battle in 490 BC in which the Athenians and their allies defeated the Persians;
Synonyms: battle of Marathon