I’m just amazed that my simple request has generated so much interest and so many posts. Thanks to everyone who has spent time considering this question and for all your helpful suggestions. I’m reasonably satisfied with the translation. Dolly, Dolby or Dobby are all feasable interpretations. I’m also satisfied to learn that I was wrong in initially suspecting the original IGI transcript submitter might have invented Oberdollyland.
The OPR sources are proof enough to me that such a place is/was located in the Langholm area or a neighbouring parish. The reference to Dolbyland Holm suggest to me that there were two farms, Upper/Over Dollyland and Dollyland-holm. [ Home or Main is what we would call today the home farm. Upper/Over/Nether are still found representing other farm leases with a larger estate.
Thanks again everyone – I’m now resorting to the old solution to genealogical brick walls.
Stopping looking and someday you or someone else will happen across the answer.