sharepoint online – Display column names in the Content Query Web Part

I've tried to find resources to describe how to insert column names into a content query web part. I understand how to add extra columns by modifying the itemstyle.xsl and query Web Part files, and have successfully inserted additional columns into my results. What I'm looking for is a way to "flag" those results.

Example:
Use the CQWP to display items from a contact list.

Columns like: location, address, manager

CQWP correctly displays the values ​​of each column, but does not give me the option to display the column name as well.

Results:

Property A

123 main street

Sally Smith

I want to display the results like this:

Site (column name)

Property A

Address (column name)

123 main street

Manager (column name)

Sally Smith

Any help to point me in the right direction would be very grateful.