Also came across Maes down here in Somerset. Maes Knoll is situated about a mile from Stanton Drew circles, and is an important landscape feature. Probably you could see it from the circles but have never checked, it has the Wansdyke running up to it, and a hillfort I think. When I looked at the name in the Anglo saxon dictionary, maeg stood at the beginning of a lot important words, maegan-cyning- mighty king; maegan-cyning - mighty burden; maegp - maiden. Maeres - valley of the boundary; maerlic - glorious; maesse - mass; and then you come to this maest - see micel which means great and maest which means greatest. So Maes knowe obviously comes under this heading. Though of course all the aforementioned are from the saxon who presumably never made it to Scotland! So will be of little help, but interesting;
Welsh; Maen - a stone; maes - field; Mam (gaelic) a large round hill; Mawr (welsh) great.
Think there is a good gaelic dictionary on Amazon (foreword by Peter Berriford Ellis)