Hey b-summers,
Thanks for stopping by. Within MailChimp, the default merge tag is designed to serve as a placeholder for a field if the subscriber doesn’t have a value for that specific field. For example, the default merge tag for a First Name field might be something like “Valued Customer”, so that if the merge tag for the First Name field is used in a MailChimp campaign, folks within a first name stored in the list will still receive a greeting of “Valued Customer” instead of a blank space.
Because MailChimp is an email marketing platform, everyone stored on the list should have an email address and wouldn’t need a default merge value for that field. Having the option to easily use the field name instead of the default merge value as the placeholder seems like it would be pretty handy, and I’ve passed along the feature request to our developers as a suggestion for a future update. In the meantime, it would be possible to use the field name by editing the mailchimp_widget.php as noted by sem101 above.
Thanks again for posting. Please feel free to let us know if you have any other questions. Have a great day!
-Gunter