This concept is the “Shema Doctrine, based on “echad” in Deut. 6:4-5 “Hear, O Israel: The LORD our God is one LORD:”
The English word “Lord” comes from the Hebrew word “YHVH” and the word “God” from “Elohim” (0430 Strong concordance). The other English translation referring specifically to YHVH is Adonai or El Shaddai. By the way, there is no upper case in the original.
This uni-plural Hebrew word “elohim” means”multiplicity of powers”, plurality of powers or majesty, the most supreme of all powers”, otherwise Supreme God, the epitome of all. Contextually, “above all gods” in Ps 95:3; 96:4; 97:9; 135:5; I Chron.16:25. The possessive words “us” and ” our” in Genesis 1, were not in the original Hebrew but translated as such for “grammatical consistency”.
Moreover, “elohim” is a common or generic term, not a proper noun nor a specific term for a particular being. It occurs more than 2500 times in the Hebrew Bible, with meanings ranging from “gods” in a general sense (as in Exodus 12:12, where it describes “the gods of Egypt”), to specific gods (e.g., 1 Kings 11:33, where it describes Chemosh “the god of Moab”, or the frequent references to Yahweh (Jehovah) as the “elohim” of Israel), to demons, seraphim, and other supernatural beings, to the spirits of the dead brought up at the behest of King Saul in 1 Samuel 28:13, and even to kings and prophets (e.g., Exodus 4:16).The KJV has “elohim” translated as “judges” in Exodus 21:6; Exodus 22:8; and twice in Exodus 22:9.
These are “other gods”albeit “false gods” that definitely must not be worshipped as that would be tantamount to idolatry.
To be specific, this Elohim was further identified as the one and only “YHVH” (Yahweh) translated as “Lord” in Genesis 2; i.e., “YHVH ELOHIM” or “Lord God”. This is the Creator God referred to also in John 1 as LOGOS, who incarnated to man-Jesus, Yeshua or YHVH ELOHIM and was called “God” (John 1:1; 20:28; Titus 2:13), the “same yesterday, today and forever”(Heb.13:8). “YHVH ELOHIM” is the specific and proper name of the one true God of Israel. Much like “Smith” is generic or common name, but the proper name is the one and only “John Smith”. YHVH ELOHIM” is above all “gods”(Ps 95:3; 96:4;97:9;135:5; Ex. 15:11; IChr. 16:25)
Another name that is specific to the person is the Hebrew word “Adon” (singular) Adown, or “Adonim” (plural), Adonai. This is translated into English as “Lord” in the OT (Ex.34:23), the God of Israel. There was no attempt to duplicate this Hebrew in the NT.
In the New Testament, however, the English word “God” comes from the Greek word “Theos” and in general refers to the Father. Whereas, the English word “Lord” comes from the Greek word “kyrios”, and refers specifically to Jesus. Notice that Hebrew word “YHVH” and Greek word “Kyrios” are both translated into English word “Lord”, referring to Jesus, who is also Logos or Word in John 1.
A definitive separation and distinctiveness of these words can be proven in:
I Cor 8:6 “But we know that there is only one God, the Father, who created everything, and we live for him. And there is only one Lord, Jesus Christ, through whom God made everything and through whom we have been given”.
I Tim. 2:5″There is one God, and one mediator also between God and men, the man Messiah Yeshua” .
Ps. 2:7:”You are my son; today I have become your father”. Not yesterday or tomorrow but “today”, “this is my beloved Son in whom I am well pleased” (Matt.3:17;Mk.1:11).
John 5:37 “And the Father who sent me has himself testified concerning me. You have never heard his voice nor seen his form”.
Jesus himself said that no one has seen nor heard the Father referred to in the New Testament. Conversely, all the time from Genesis on, the specific “elohim” had to be YHVH ELOHIM, the LOGOS according to John, who incarnated to man-Jesus (anthropos-Jesus to Paul), the Messiah Passover.
In short, “The Lord is one” refers only to YHVH ELOHIM not the FATHER of Jesus and of us all.