The Hebrews would not speak the name of Yahweh/Jehovah and instead reduced his name to YHWH by eliminating the vowels. This abbreviation was called "the tetragrammaton" because it consists of four letters.
The followers of MY God, the one true God, have likewise reduced his name, but to THREE letters. This is called the trigrammaton and is FSM.
For sacred reason I cannot tell you more about him here but should you choose to Google FSM you will learn enough to put you into a meaningful relationship with Him.