Yes, it was. We've only fairly recently actually 'proven' the existence of planets orbiting other stars. Also, our star's name is (as far as I know) considered to be Sol, so the term Solar system may in fact only apply to our own (
wikipedia says not, however). Planets orbiting around Betelgeuse might be called the Betelgeus(ian?|e) system.
Also, the milky way originated as the term for the way it looked in the sky, so it's not exactly unoriginal as much as just what it came to be known as....