The source of a column in a content type can be retrieved in the User Interface as follows:
- Go to List Settings
- Click on Advanced Settings, set Allow Management of Content Types to Yes and click OK to return to the List Settings page
- The Content Types section should now be visible. Click on the content type to view the columns in the content type
- If the column comes from the content type's parent (or ancestor), the "source" will be marked with the appropriate content type.
Example: for a calendar list, the Source of the Title column will be Item, the Source of Location, Start Time, End Time, etc. will be Event, and the source of any columns manually added to the list will be blank.
How can the "Source" be retrieved programatically - i.e. C# (SSOM/CSOM), PowerShell, etc.