just back from Norway, and Helge said that he has no idea what "maes" could be, but that "howe" in Norwegian means a man-made hill, with several different applications. a barrow would be a howe, as would the spoil-heap created by digging a hole, or even a pile of logs produced by chopping wood.

so how about Mages (Celtic) and Howe (Norwegian) - plain of the man-made hill?

Cheers
Andy