Tuesday: The most important of God's Names is the four-letter Name represented by the Hebrew letters Yod-Hei-Vav-Hei (YHVH). It is often referred to as the Ineffable Name, the Unutterable Name or the Distinctive Name. Linguistically, it is related to the Hebrew root Hei-Yod-Hei (to be), and reflects the fact that God's existence is eternal. In scripture, this Name is used when discussing God's relation with human beings, and when emphasizing his qualities of lovingkindness and mercy. It is frequently shortened to Yah (Yod-Hei), Yahu or Yeho (Yod-Hei-Vav), especially when used in combination with names or phrases, as in Yehoshua (Joshua, meaning "the Lord is my Salvation"), Eliyahu (Elijah, meaning "my God is the Lord"), and Halleluyah ("praise the Lord").

The first Name used for God in scripture is Elohim. In form, the word is a masculine plural of a word that looks feminine in the singular (Eloha). The same word (or, according to Rambam, a homonym of it) is used to refer to princes, judges, other gods, and other powerful beings. This Name is used in scripture when emphasizing God's might, His creative power, and his attributes of justice and rulership. Variations on this name include El, Eloha, Elohai (my God) and Elohaynu (our God).

God is also known as El Shaddai. This Name is usually translated as "God Almighty," however, the derivation of the word "Shaddai" is not known. According to some views, it is derived from the root meaning "to heap benefits." According a Midrash, it means, "The One who said 'dai'" ("dai" meaning enough or sufficient) and comes from the fact that when God created the universe, it expanded until He said "DAI!" (perhaps the first recorded theory of an expanding universe?). The name Shaddai is the one written on the mezuzah scroll. Some note that Shaddai is an acronym of Shomer Daltot Yisrael, Guardian of the Doors of Israel.

Another significant Name of God is YHVH Tzva'ot. This Name is normally translated as "Lord of Hosts." The word "tzva'ot" means "hosts" in the sense of a military grouping or an organized array. The Name refers to God's leadership and sovereignty. Interestingly, this Name is rarely used in scripture. It never appears in the Torah (i.e., the first five books). It appears primarily in the prophetic books of Isaiah, Jeremiah, Haggai, Zechariah and Malachi, as well as many times in the Psalms.
Writing the Name of God

Jews do not casually write any Name of God. This practice does not come from the commandment not to take the Lord's Name in vain, as many suppose. In Jewish thought, that commandment refers solely to oath-taking, and is a prohibition against swearing by God's Name falsely or frivolously (the word normally translated as "in vain" literally means "for falsehood"). .................

With the Temple destroyed and the prohibition on pronouncing The Name outside of the Temple, pronunciation of the Name fell into disuse. Scholars passed down knowledge of the correct pronunciation of YHVH for many generations, but eventually the correct pronunciation was lost, and we no longer know it with any certainty. We do not know what vowels were used, or even whether the Vav in the Name was a vowel or a consonant. See Hebrew Alphabet for more information about the difficulties in pronouncing Hebrew. Some religious scholars suggest that the Name was pronounced "Yahweh," but others do not find this pronunciation particularly persuasive.

Some people render the four-letter Name as "Jehovah," but this pronunciation is particularly unlikely. The word "Jehovah" comes from the fact that ancient Jewish texts used to put the vowels of the Name "Adonai" (the usual substitute for YHVH) under the consonants of YHVH to remind people not to pronounce YHVH as written. A sixteenth century German Christian scribe, while transliterating the Bible into Latin for the Pope, wrote the Name out as it appeared in his texts, with the consonants of YHVH and the vowels of Adonai, and came up with the word JeHoVaH, and the name stuck.

http://www.jewfaq.org/name.htm

It's just a best guess name.