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