YHWH
יהוהthe four letters- Means
- Unknown with certainty, and connected in Exodus to the verb to be: I AM WHO I AM, or I WILL BE WHAT I WILL BE. The Hebrew allows both, and the ambiguity may be deliberate.
- Where you meet it
- Given to Moses at the burning bush, when he asks what to say if they ask the name.
This is a name, not a title. It belongs to this God and to no other, which is why the commandment about not taking it in vain exists at all. Out of reverence, readers came to say Adonai, my Lord, instead of pronouncing it, and English translators followed that practice by printing LORD in small capitals wherever the four letters stand. So the typography is a translation decision about reverence, made visible.
That also explains the strange-looking phrase the Lord GOD. The Hebrew there is Adonai YHWH; printing it as Lord LORD would read as a mistake, so the second word is set as GOD instead. Jehovah is a hybrid form, made by combining the consonants of the name with the vowels of Adonai, and few scholars now think it was ever pronounced that way.