You guys are going to love this...
IT WAS MY CHIROPRACTOR. Apparently they have new owners, or the owners got a new card processing service, something like that.
Alas, that information came too late to prevent debit card #2 from being cancelled. I called my CU this morning, explained in brief what was up, and the rep said that we'd have to cancel the new card. I replied "well can I talk to someone who can look into this in more depth?" and she said she'd see if anyone in loss prevention could take the call, and put me on hold. Apparently while I was waiting she cancelled my card and transferred me to a very nice woman who had a heck of a time finding the 1st transaction on my old card. So she talked to card services and called me back. Seems that with their help, she was able to get the merchant ID from the transaction, and found out it was a chiropractic service.
I called the chiropractor and lodged a complaint about the new name appearing on the card transactions. It seems I am far from the first to complain. And I get to wait another week for yet another new debit card.