The question is about the half asteroid, half comet centaurs. They were not named after Centaurus.

Well, presumably some guy/gal named them cuz they reminded him/her of half men half horses. As I asked: do you have some other examples of this phenomenon? If not, I hardly think it needs a term that covers the coining of this particular word. Metaphor covers it pretty well, but seems broader than expected.

Ceci n'est pas un seing.