Why is Earth the solitary planet bypassing divine nomenclature?

It was the fixed center of observation, not perceived as a celestial wanderer.

Earth is unique in the solar system because it was not named after a Greek or Roman deity, unlike every other major planet extending out to Neptune. This exemption stems entirely from the ancient observational perspective. The other planets were observed as 'wanderers'—celestial lights moving against the fixed background of stars, leading ancient people to naturally ascribe characteristics of powerful governing deities to them. Earth, however, was the opposite: it was the fixed entity, the ground beneath their feet, the very stage upon which the observed cosmic drama unfolded. Because it was the known, fundamental entity, it did not require a celestial appellation or personification as a distant god; its name evolved organically from terrestrial linguistic roots meaning 'ground' or 'soil,' existing outside the framework of classical divine nomenclature.