Isn't it much the same as Vulcan or Vulcanian?
“Vulcanian” was used early in Trek TOS. I believe the last episode in which it was heard was “Court Martial.” Since “Vulcan” sounded like an adjective anyway, it was simpler to use the same word for both the planet and its inhabitants.
Actually, come to think of it, Vulcans should be from the planet Vulc.
. . . I do remember that I had to stand up in front of my 8th grade English class to give a report or something, and I must have made the subject Star Trek . . .
I gave an oral report on Star Trek
in my 11th grade Spanish class -- in Spanish. Hell, the whole school already knew I was one of the geeks.