What does Aria mean?
From the Italian word 'aria', meaning 'air' and, in music, a solo melody or song. An identical-looking name also exists in Hebrew (related to 'aryeh', lion) and Persian, but the modern popularity rests on the Italian 'melody' sense.
What does Bella mean?
Directly the Italian/Spanish word bella 'beautiful', from Latin bella/bellus. NOTE: as a given name Bella is most often a short form of Isabella, whose own meaning is 'pledged/devoted to God' (a Hebrew-origin name, NOT beauty); Bella qualifies here only on the strength of the standalone Italian word 'beautiful'.