Vulcanoids

Continued attention to the Vulcan theme has disclosed the theory of Vulcanoids. Poul Anderson's Vulcan is not a Vulcanoid, an asteroid permanently orbiting close to the Sun, but an asteroid passing close to it.

OK. I understand how the meaning of "Vulcan" came to be stretched and changed both in works of fiction and in our world where the fictions are written:

it was hypothesized that there was a planet closer to the Sun than Mercury;

this hypothetical planet was appropriately named "Vulcan";

the existence of such a planet was disproved;

this freed the name "Vulcan" to be applied to any other planet discovered later;

maybe it was remembered that there had been a hypothetical solar planet, Vulcan, but not that this name implied proximity to the Sun;

thus, somebody came to say, "Here is that hypothetical other solar planet, Vulcan, even though it is not located where it was originally thought to be in the System."

The meanings of words and names do change over time. When rereading World In Eclipse (1954), I thought it unlikely that abductees taken to Hafna would call that planet "Vulcan" rather than just accepting the natives' name for it. However, the text clearly states:

"Terrestrial astronomers had given [Vulcan] that name since their year number 1960, when they first saw it with their astronomical instruments."
-William Dexter, World In Eclipse (London, 1962), CHAPTER TWO, p. 9.

That is the explanation. Meanwhile, Anderson got it right that, if an asteroid passed within the orbit of Mercury, then it would be called "Vulcan" after the god, the hypothetical planet or both.