The etymology of the word “planet” actually comes from late Old English planete, from Old French planete (Modern French planète), from Latin planeta, from Greek planetes, from (asteres) planetai “wandering (stars),” from planasthai “to wander,” of unknown origin, possibly from PIE *pele “flat, to spread” or notion of “spread out.” And Plane ( n ) “flat surface,” c. 1600, from Latin planum “flat surface, plane, level, plain,” planus “flat, level, even, plain, clear.” They just added a “t” to our Earth plane and everyone bought it.