Vulcan was already the name suggested for a hypothetical planet closer to the sun than Mercury. One motivation for the hypothesis was an observed discrepancy in Mercury’s perihelion precession compared to Newtonian predictions using the known planets, but then general relativity perfectly predicted the discrepancy without requiring an extra planet.
George would have some confusion about the “planet Vulcan” bit long before Star Wars, though.
Vulcan was already the name suggested for a hypothetical planet closer to the sun than Mercury. One motivation for the hypothesis was an observed discrepancy in Mercury’s perihelion precession compared to Newtonian predictions using the known planets, but then general relativity perfectly predicted the discrepancy without requiring an extra planet.