Christian name 
noun
A first name, especially one given at baptism: she was not used to addressing adults by their Christian names his Christian name is Gerry...
- The chumminess of members referring to each other by their Christian names in debate is meant to signify democratic informality.
- I always called him ‘boss’, never by his Christian name.
- May I also draw attention to the unacceptable use of initials, instead of full Christian names.
Usage
In recognition of the fact that English-speaking societies have many religions and cultures, not just Christian ones, the term Christian name has largely given way, at least in official contexts, to alternative terms such as given name, first name, or forename.