Tetragrammaton

the four consonants of the ancient Hebrew name for God (variously transliterated JHVH, IHVH, JHWH, YHVH, YHWH), that was considered too sacred to be spoken aloud: the word Adonai (Lord) is substituted for this name in utterance, and the vowels of Adonai or Elohim (God) are inserted in Hebrew texts, so that the modern reconstructions are Yahweh, Jehovah, etc.