"The Holy One, Blessed be He, has any number of names.
All of these names, however, designate only various aspects of divine manifestation in the world, in particular as these are made known to human beings.
Above and beyond this variety of designations is the divine essence itself, which has not, and cannot have, a name.
We call this essence, or God-in-Himself, by a name that is itself a paradox: 'the Infinite, Blessed be He.'
This term, then, is meant to apply to the divine essence in itself, which cannot be called by any other name since the only name that can be applied to the very essence of God must include both the distant and the near--indeed everything.
Now as we know, in the realms of abstract thought, such as mathematics and philosophy, infinity is that which is beyond measure and beyond grasp, while at the same time the term is limited by its very definition to being a quality of something finite.
Thus, for example, there are many things in the world such as numbers, that may have infinity as one of their attributes and yet also be limited either in function or purpose or in their very nature.
But when we speak of the Infinite, Blessed be He, we mean the utmost of perfection and abstraction, that which encompasses everything and is beyond all possible limits."
From "Divine Manifestation," in The Thirteen Petalled Rose by Rabbi Adin Steinsaltz