What does Kiara mean?
Etymologically a variant of Italian Chiara, from Latin 'clara' meaning 'bright, clear'. In English-speaking use the identical spelling overlaps with the Irish Ciara (from 'ciar', dark), producing a genuine opposite-meaning clash: the Italian root means 'bright' while the Irish association means 'dark'.
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'.