The name “Earth” is derived from both English and German words, ‘eor(th)e/ertha’ and ‘erde’, respectively, which mean ground. But, nobody knows who named our planet Earth. Earth is the only planet that wasn’t named after a Greek or Roman god or goddess. For example, Saturn was named after the Roman god of agriculture, and Jupiter’s name comes from the King of the Roman gods.
Source: how did earth get its name