On distinguishing between God's personal name and His official titles: the Watchtower society's commentary..

 Wol.Jw.org

In its articles on JEHOVAH, The Imperial Bible-Dictionary nicely illustrates the difference between ʼElo·himʹ (God) and JEHOVAH. Of the name JEHOVAH, it says: “It is everywhere a proper name, denoting the personal God and him only; whereas Elohim partakes more of the character of a common noun, denoting usually, indeed, but not necessarily nor uniformly, the Supreme. . . . The Hebrew may say the Elohim, the true God, in opposition to all false gods; but he never says the JEHOVAH, for JEHOVAH is the name of the true God only. He says again and again my God . . . ; but never my JEHOVAH, for when he says my God, he means JEHOVAH. He speaks of the God of Israel, but never of the JEHOVAH of Israel, for there is no other JEHOVAH. He speaks of the living God, but never of the living JEHOVAH, for he cannot conceive of JEHOVAH as other than living.”​—Edited by P. Fairbairn, London, 1874, Vol. I, p. 856.

The same is true of the Greek term for God, The·osʹ. It was applied alike to the true God and to such pagan gods as Zeus and Hermes (Roman Jupiter and Mercury). (Compare Ac 14:11-15.) Presenting the true situation are Paul’s words at 1 Corinthians 8:4-6: “For even though there are those who are called ‘gods,’ whether in heaven or on earth, just as there are many ‘gods’ and many ‘lords,’ there is actually to us one God the Father, out of whom all things are, and we for him.” The belief in numerous gods, which makes essential that the true God be distinguished from such, has continued even into this 21st century.

Paul’s reference to “God the Father” does not mean that the true God’s name is “Father,” for the designation “father” applies as well to every human male parent and describes men in other relationships. (Ro 4:11, 16; 1Co 4:15) The Messiah is given the title “Eternal Father.” (Isa 9:6) Jesus called Satan the “father” of certain murderous opposers. (Joh 8:44) The term was also applied to gods of the nations, the Greek god Zeus being represented as the great father god in Homeric poetry. That “God the Father” has a name, one that is distinct from his Son’s name, is shown in numerous texts. (Mt 28:19; Re 3:12; 14:1) Paul knew the personal name of God, JEHOVAH, as found in the creation account in Genesis, from which Paul quoted in his writings. That name, JEHOVAH, distinguishes “God the Father” (compare Isa 64:8), thereby blocking any attempt at merging or blending his identity and person with that of any other to whom the title “god” or “father” may be applied.