How to add get the field name for a newly added site column.

I have the following:-

1. Enterprise wiki site collection inside SharePoint server 2013.
2. I added a new site column of type managed metadata.
3. I opened the enterprisewiki.aspx page layout using the SP designer, to add the newly added site column to it.

But I have noted that to add any site column I need to know the field name , for example the default wiki category column is referenced inside the page layout as follow:-

<Taxonomy:TaxonomyFieldControl FieldName="Wiki_x0020_Page_x0020_Categories" EmptyValueDescriptionForTargetTemplate="<%$Resources:cms,enterwiki_nocategories_assigned%>" DisableInputFieldLabel="true" runat="server"/><b>

Thanks in advance for any help.

Regards