Anonymous asked: What exactly is the or what does "Tetragrammaton" mean?
It’s a Greek term for the four-letter rendering of the personal name of the G-d of Israel by the Israelites, but also what some Christians use when speaking of the Father.
And, as Andrew pointed out, it is the YHWH often seen. It is the personal name of G-d, with the vowels removed, so as to show reverence and respect for the name by not permitting it to cross human lips, in much the same way that G-d has the O removed, to produce the same effect.
We get Jehovah from it by adding the vowels from Adonai, Hebrew for Lord, between YHWH. Hope that helps.