Most of the parishes had their heads in the mountains, their feet in the sea. (Not Marown, obviously). In fact Maughold had a "Mountain Third" of the Parish (see "A History of KK Maughold" p. 156.0 This was called "Cheu Clieau" lit. "Mountain Side". Mrs C K Radcliffe wrote about the "Mountaineers" who appeared rarely at Parish meetings but occasionally descended to intervene descisively. A bit like the "Backwoodsmen" in the old House of Lords!
In Lonan, I cannot see the Main Quarterlands of Gretch being termed in the Mountains, but if there were crofts at the north end, which merged into intacks, then this woukd be more likely. Crofts would be smaller portions of quarterlands - some were fragmented as early as 1490/1511. Others were occupied by sub-tenants.