XML field for user name invoking the document merge?

Hi All,

I'm using CRM Online 2016 and my objective is to create a Word merge document that extracts quite a bit of data from a Contact entity when doing the merge. This works well.

However, I also want to add a signature line where the invoking CRM user's full name would be shown. It seems I cannot find the correct XML field for this. I can get the full name of the user who created the contact originally etc, but the current user name field is elusive. What is the correct field for this?

Thanks in advance.