Making A Custom Field for a Digital Product That's Been Purchased

I am setting up a purchase action to send a customer an Order Receipt.

I would like to Merge a field for the Product that they are purchasing.

Is there a custom field I can merge that is for the product? I have the individual Products showing as Merge Tags under “Digital Products”, but I would like to automate this so that customers get the right product named in this email.

I presume it would be something like this: ~Contact.FirstName~, but for the name of the Product they’ve purchased.

Thanks for pointing me in the right direction.