Most words ending with -vious are from Latin *via*, "road, way*, including "obvious" (in the way), "impervious" (no way thru), "devious" (off the way, cf. deviate), and "previous" (before on the way)

Most words ending with -vious are from Latin via, "road, way*, including "obvious" (in the way), "impervious" (no way thru), "devious" (off the way, cf. deviate), and "previous" (before on the way)

The similarity of "envious" and "oblivious" is coincidental:

envious is just envy + -ous, where envy is from Latin invidia "envy".
oblivious is from Latin obliviosus, from oblivium "forgetfulness" + -osus "-ous".

Edit: changed the title from "previous" (ahead on the way) beacause I apparently forgot what pre- means lol