marathonyoudaoicibaDictYouDict[marathon 词源字典]
marathon: [19] According to tradition, when the Greek army defeated the Persians at Marathon, on the northeast coast of Attica, in 490 BC, the runner Pheidippides was dispatched to bring the good news to Athens (in fact there is no contemporary evidence for the story, which is not recorded until 700 years after the event). When the modern Olympic Games were first held, in Athens in 1896, a long-distance race was introduced to commemorate the ancient feat, run over a course supposedly equal in distance to that from Marathon to Athens (about 35 km/22 miles).

The present distance (42.195 km/26 miles 385 yards) was established at the 1908 London Olympics (the odd yards were added to bring the finishing line in front of the royal box).
[marathon etymology, marathon origin, 英语词源]