HTTP is not a madeup word. Neither is
Loopback. While the combination
HTTP Loopback may not be made up, Google doesn't seem to find it anywhere except in connection with
Backup Buddy and according to the links I've been able to find, the Backup Buddy people simply say to contact your hosting company and have them set it.
Biut no one else defines it, and no other entity, hosting company or other, appears to define it. So I'd tend to agree with user scsi that we'll need to consider it a made-up word.
Ask the people at Backup Buddy exactly what to ask your hosting company to do, or live with the problem or find a solution.
Or of course just make up an answer
In other words, they're calling something
HTTP Loopback but no one else calls it that, so unfortunately it doesn't seem possible to give you a definitive answer.
Jeff