Cruel and nasty, we shall be. As the name may have only referred to the summit, the answer may be as simple as Ilmarin, which are the halls built upon the summit.
However, considering 'Oiolosse' was simply the most common name used, there are also Amon Uilos, Mount Everwhite, the White Mountain, the Holy Mountain, Elerrina, the Hill of Ilmarin, and the Mountain to choose from.
Fea
[has handy dandy references]