planetyoudaoicibaDictYouDict[planet 词源字典]
planet: [12] A planet is etymologically a ‘wanderer’. The word comes via Old French planete and late Latin planēta from Greek planétos, a derivative of the verb planasthai ‘wander’. This was applied to any heavenly body that appeared to move or ‘wander’ across the skies among the fixed stars, which in ancient astronomy included the sun and moon as well as Mars, Venus, etc. The modern application to a ‘body that orbits the sun (or similar star)’ dates from the mid 17th century.
[planet etymology, planet origin, 英语词源]
planet (n.)youdaoicibaDictYouDict
late Old English planete, from Old French planete (Modern French planète), from Late Latin planeta, from Greek planetes, from (asteres) planetai "wandering (stars)," from planasthai "to wander," of unknown origin, possibly from PIE *pele- (2) "flat, to spread" on notion of "spread out." So called because they have apparent motion, unlike the "fixed" stars. Originally including also the moon and sun; modern scientific sense of "world that orbits a star" is from 1630s.