meridianyoudaoicibaDictYouDict[meridian 词源字典]
meridian: [14] Etymologically, meridian denotes the ‘middle of the day’. It comes via Old French from Latin merīdiānus, a derivative of merīdiēs ‘mid-day’. This was an alteration of an earlier medidiēs, a compound noun formed from medius ‘middle’ (source of English medium) and diēs ‘day’. The application of the word to a circle passing round the Earth or the celestial sphere, which is an ancient one, comes from the notion of the sun crossing it at noon.
=> medium[meridian etymology, meridian origin, 英语词源]
meridian (n.)youdaoicibaDictYouDict
mid-14c., "noon," from Old French meridien "of the noon time, midday; the Meridian; southerner" (12c.), and directly from Latin meridianus "of midday, of noon, southerly, to the south," from meridies "noon, south," from meridie "at noon," altered by dissimilation from pre-Latin *medi die, locative of medius "mid-" (see medial (adj.)) + dies "day" (see diurnal). Cartographic sense first recorded late 14c. Figurative uses tend to suggest "point of highest development or fullest power."

The city in Mississippi, U.S., was settled 1854 (as Sowashee Station) at a railway junction and given its current name in 1860, supposedly by people who thought meridian meant "junction" (they perhaps confused the word with median).