What is the pattern used to name the fields accessible through the API?
For historical reasons (namely cramming a bunch of fields from various entities into a flat array for e.g. a profile form) some fields in the database have a "unique_name" which is generally the entity prefixing the field name. For obscure reasons, the api v3 sometimes returns those "unique_names" instead of the regular field names.

I personally hate the implementation of unique names in CiviCRM - it's inconsistent and confusing and if I have anything to say about it there will be no unique names in api v4!