*Earth is also used as a synonym for dirt (called regolith on other planets and moons). Earthlings. Terra is the Latin word. Terrans..
Yes, of course. "Terran" was coined by science fiction writers as a demonym for Earth people analogous to national demonyms like "Mexican" or "Albanian." It caught on as a classier-sounding alternative to "Earthling." It's generally used as a term that aliens or members of an interstellar human civilization use to refer to Earth humans, which is why DS9 had the Klingon-Cardassian Alliance refer derogatorily to humans as "Terrans" (an intention misunderstood by
Enterprise's writers when they dubbed the Mirror Universe Empire the "Terran Empire," and even more greatly misunderstood by
Discovery's writers when they started using "Terran" as a term
exclusively for Mirror humans, even though prior Trek had often use it to refer to Earth people in the Prime universe).
But "Terran" is an etymologically suspect coinage. A more authentically derived term would be "Tellurian," a word sometimes used in
Doctor Who serials by Robert Holmes.
Vulcans (Vulcanians) from Vulcan
Bajorans (Bajora) from Bajor
Andorians from Andor
Betazoids from Betazed
Deltans from Delta
Ferengi from Ferenginar
Earthlings from Earth, Terrans from Terra
But Klingons from Kling? Nah, that's silly.
The point, I believe, is that they're
all silly. It seems implausible that a culture would name itself after its planet, or vice-versa, since its people would've coined their name before they thought of their planet as a single entity defined in relation to alien planets. Names like that are more likely to be assigned by outsiders, so it stands to reason that the indigenous name or names would be different.
At least, that's what I thought until I learned the etymology of "human," as I mentioned above. Even so, the words "Earth" and "human" sound different despite their common origin, because we have more than one language on Earth, and aliens surely would as well.