The default behavior for how the Salesforce B2B Commerce Global APIs transform Salesforce data is to return field names with a lowercase first letter, camelcase convention. For example, the field name ccrz__E_Product__c in Salesforce will be transformed to eProduct in the API. This is done to follow the JavaScript naming convention and to avoid conflicts with the standard Salesforce fields and relationships. Salesforce Reference: B2B Commerce and D2C Commerce Developer Guide, Query Transformation