For me, a solar system are also called system in itself , it because , "solar" means --derived from the "Sun" -- ( Solar System means Sun and the bodies orbiting on it) "System" is the related part of sun. the asteroids,planets and other bodies.
(it is called System in itself because the planets and other bodies revolving on it )
"System" means the planets and bodies (such as asteroids, meteor and etc. anything that revolve in the sun)
and "Itself" is related to the sun.