That name he used, they aren't really sure how to pronounce it but it was attempting to use the 4 letter Hebrew word they used for God in the Temple.
(The name of God is discussed in this post so please don't print it)
The high priests had bells sewn onto their clothes and a rope tied around their leg so if they DIED while saying the Name, they'd know and could pull them out.
Judaism clearly recognizes the existence of a Name for God (we have many Names for God in the Hebrew).
The most important of God's Names is the four-letter Name represented by the Hebrew letters Yod-Heh-Vav-Heh (Hashem). It is often referred to as the Ineffable Name, the Unutterable Name or the Distinctive Name. You'll see the word Hashem, Adonai, or God in it's place in most English translations.
In Deut. 12:3, the people are commanded that when they take over the promised land, they should destroy all things related to the idolatrous religions of that region (like a mosque *cough*), and should utterly destroy the names of the local deities. Immediately afterwards, we are commanded not to do the same to our God. From this, the Rabbis logically inferred that we are commanded not to destroy any holy thing, and not to erase or deface a Name of God.
(FYI this prohibition against erasing or defacing Names of God applies only to Names that are written in some kind of permanent form, and recent rabbinical decisions have held that writing on a computer is not a permanent form but, once you print the document out, it becomes a permanent form.)
Some Rabbis asserted that a person who pronounces Hashem according to its letters (instead of using a substitute) has no place in the World to Come, and should be put to death.