God's name

When Moses asked God: Who are you?, He answered: I am the one that will be (eie asher eie in Hebrew) (Exodus 3:14). This is abreviated to four letters, YHWH, also know as the tetragrammaton. This is from the name Jehova come from (in Hebrew, vowels aren't written down, so that's how you can go from YHWH to YeHoWaH).

Another legend says that God has 100 names, each describing an attribute of Him.

The name of God, I think, is a clever pun on ancient metaphysics like Zen and Tao. See, the Tetragrammaton, Yhvh, is a word that can not be spoken but as a blow or slight breath, thus not really 'pronounced'.
Compare with the Tao Te Ching by Lao Tzu (born 604 BC, China): "The name that can be spoken is not the immutable name".
Given the nature of God as something perpetual and immutable, the only name that could represent Him is the 'name that can not be spoken': a four-letter combination that can never be pronounced.