tetragrammaton (n.)

c. 1400, from Greek (to) tetragrammaton "(the word) of four letters," from tetra- "four" (from PIE root *kwetwer- "four") + gramma (genitive grammatos) "letter, something written" (see -gram). The Hebrew divine name, transliterated as YHWH, usually vocalized in English as "Jehovah" or "Yahweh."