Earth has also been referred to as the "Blue Planet" which came from the Apollo 17 astronauts referring to earth as a "Blue Marble" and old wano looks like ancient japan. In many ways it looks like "Blue Planet" is a version of earth whose history branched off at some point before japan started to industrialize.
Its also not that uncommon for terms to become archaic over time, like how "thou" is now more or less an archaic version of the word "you". "Earth" being corrupted into "Vearth" and "Blue Planet" stocking around instead of "Blue Marble", they both easily fall into this. Hell, even the Will of D's meaning is lost of most people including those with "D".
