Tetragrammaton has 2 different meanings across 2 categories:
four Hebrew letters usually transliterated as YHWH (Yahweh) or JHVH (Jehovah) signifying the Hebrew name for God which the Jews regarded as too holy to pronounce
The four Hebrew letters יהוה (in transliteration, YHWH or JHVH) used as the ineffable name of God in the Hebrew Bible, variously transliterated as Yahweh or Jehovah.