A ("THE") Hebrew word for ("THE") God (see Hebrew words for God for some history of this and other words). It's (probably) pronounced "yahveh" (or "yahweh"), or "Jehovah" in English. The Bible vocalises it in this form. However, it is never said out loud (a custom which predates Monty Python by over 3 millenia). This is the "literal name" of God.

The explanation of the word is given by God to Moses at the burning bush. Moses has just been told to go back to the people of Israel, and tell them he's met God, etc., etc. But all the ID he got (apart from the miracle of the burning bush, but as a trained Egyptian magician he knew that any god could do that) was a (disembodied) voice claiming to be the Lord of Abraham, Isaac and Jacob. Quite rightly, he says the people of Israel will want to know who this god is, so he asks God. By way of reply, God tells him "I am what I am", adding Moses can say "I am" (AHWH, after some Semitic manipulations) sent him. And YHWH is simply the form "he is", similarly manipulated.

It is entirely possible that this story is a late formation to explain the word YHWH. But the story sounds entirely plausible (many other Semitic gods of the period have equally silly names).