What does Riya mean?
Commonly given as Sanskrit-derived riya (रिया), 'singer' or 'graceful'. It is not well attested in classical Sanskrit literature, so this meaning is popular rather than firmly documented.
What does Diya mean?
From the Hindi दीया (diyā), 'an oil lamp', descended from the Sanskrit dīpa ('lamp, light'). A genuine, everyday Hindi word evoking the lamps of Diwali.