Ineffable Name

AKA the Tetragrammaton, Divine Name or Unutterable Name.

It was forbidden to the Jews to pronounce the Tetragrammaton or Sacred Name of God; a reverential usage which is also observed in Masonry.  Hence the Tetragrammaton is called the Ineffable Name.  As in Masonry, so in all the secret societies of antiquity, much mystery has been attached to the Divine Name, which it was considered unlawful to pronounce, and for which some other word was substituted.  Adonai was among the Hebrews the substitute for the Tetragrammaton. (See Encyclopedia of Freemasonry by Mackey)