what is your good name? is used to ask in appreciation, i think.

what's your good name ? using this kind of sentence is inappropriate because it's not acceptable. mainly it's very popular in our India that people ask what your good name is ? as far as I know we should avoid using it.

yes, it is in the sense your original name not pet name.

It is customary to ask 'aap ka shub naam kya hai' in hindi.then why don't we translate it to ask anyone politely.

'What is your good name?' this question asked when someone want to know your full name. Full name means - your name and your sir name (caste).