The short answer is 'No'. I cannot see any way of doing what you want with Apple software or anything free. It is possible you might be able to do it in Microsoft Office but I have not checked.
As a workaround, this is what I would do:
1. Create a new account on your Mac. Let's call it 'Xmas' for this exercise
2. From your normal account, export a vcard file of all your AddressBook contacts (or just your Christmas card list)
3. Go to Macintosh HD/Users/Xmas/Public/DropBox and drop that vcard.vcf file in there
4. Open up your Xmas account from the menu bar (you can keep your other account running too)
5. Launch AddressBook and import the vcard data from the drop box (or move the file somewhere convenient)
6. Change the Given name of all cards in your Christmas card list to 'The'
7. Print labels
The Xmas account can stay dormant from one Christmas to the next.
Hi. I am a new Mac user and I need help with mailing labels. When I print my labels, I want to use a custom field - Label Name - as the first line on the label, rather than the name of the contact. Is there a way to do this? For example, I might have a contact name of Joe Johnson, but I will have The Johnsons as his Label Name for sending holiday cards, etc. I don't want to change all my contact names to these appropriate label names. Is there a way to configure the mailing label to print the custom field rather than the first and last name? Thanks for your help.