You may have noticed that in English translations of the Bible, particularly the Old Testament, the word “LORD” (in all capital letters) appears often. Why is this?
It goes back to the Jewish reluctance to write or use the personal name of God. In Exodus 3, when God reveals Himself to Moses, Moses asks God for His name. God says to Moses, “I am who I am.” His people therefore called God “Yahweh,” meaning “He who is” or “He who causes to be.” The name “Yahweh” is therefore a response to God’s statement “I am who I am” and reflects His name back to Him (as a corollary, all proper theology is really a reflection back to God of what He has first revealed to us, but that’s a topic for a different time).
The original Hebrew Old Testament was written without vowels; that is, the text only contained consonants. God’s personal name was written with the four Hebrew consonants which are transliterated as “YHWH.” This four letter word is the “tetragrammaton.” When the Hebrews would read the tetragrammaton, however, they would say the Hebrew word for “Lord,” which is Adonai, rather than saying “Yahweh.” Later, in fact, when vowels were added to the Hebrew text the vowels for Adonai were placed with the tetragrammaton as a reminder to say the word “Adonai” rather than the word “Yahweh.” This caused confusion with some early English translations which did not make this switch, but rather combined the vowels for Adonai with the consonants of YHWH, giving an English pronunciation of “Jehovah” (i.e. the y/j sound of Y, plus the ah sound of A, plus the v sound of W, plus the ah sound of the last vowels of Adonai).
However, as I mentioned, the word “Adonai” (or Lord) was used as a stand-in for YHWH or Yahweh. When the Hebrew text was translated into Greek in the 3rd century BC (the Septuagint or LXX version), the Greek word for Adonai, or Lord, was used for YHWH. This Greek word is “Kyrios.” Thus, when people in the New Testament call Jesus “Lord” or “Kyrios” they are implicitly connecting him with YHWH of the Old Testament. That is, by calling him Kyrios – due to the connection between Kyrios/Adonai/Yahweh – they are also calling him Adonai and Yahweh (YHWH); i.e. he is the same God of the Old Testament, now come in the flesh and revealing the Trinity more fully.
When the Bible was translated into English there was, and still is, a desire with the Old Testament text to differentiate when the word “Yahweh” is actually used and when the word Adonai is used in the sense of “Lord,” rather than as a stand-in for Yahweh. Therefore, our English translations use LORD in all caps to identify when Yahweh is present in the original text and use Lord in lowercase to identify when the word Adonai is present in the text.
As a related note, we sometimes refer to God with the title of “Lord of Hosts.” This is actually “LORD of Hosts,” or “Yahweh Sabaoth.” The word Sabaoth has the sense of “armies” or “mighty host” (in a military sense). The ancient Greek translation, the LXX/Septuagint, translated this word as “Almighty,” thus giving a meaning of “He who is Almighty.” The Greek version of “Lord of Hosts” is “Pantokrator,” and Christ is depicted as “Pantokrator” in many icons (such as the one in this post).
I hope this short explanation is helpful and gives you some more to think about as you read the Bible.
(Image: Icon of Christ Pantocrator from Macedonia, By Unknown – Unknown, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5820582 )