Vanity is irreverence toward the Lord. The Almighty God is our Father and to him we owe everything. If his name is said it must be with deep respect. Even the substitution of benign words when thinking is irreverent because God is holy! We are commanded to honor God by Law:
Genesis 20:7 "Thou shalt not take the name of the Lord thy God in vain; for the Lord will not hold him guiltless that taketh his name in vain."
Let's get technical for a moment. God is without name. He just IS because when asked his name his response was I AM. However, God is called by many titles:Adonai, Emmanuel, Jehovah, Lord, Father, God, and so forth. There are hundreds. None is his name! How can it be then that we can take the Lord's name in vain? Technically we can't because he has no name. Giving him a name when he has no name is vanity, because we are presumptuous.
Let's say for instance, we meet Queen Elizabeth. Her name is Elizabeth, but her title is Your Majesty. If a person called her Elizabeth, the queen would be upset because there would be a lack of respect. Even more troublesome would be to call her Beth, Liz, Lizzy, or even Queen or Queenie! Any such names would be offensive to the monarch because it would minimize her authority.
Then what is the meaning of the Hebrew word where the translators have imposed "name"? It is shem, meaning to defame God's individuality. Even the word "individual" is irreverent! God is neither a person nor an individual. He just IS! Perhaps "authority" is better because God certainly has that and is due worship for having it.
Then the intent is not to trivialize God's position of authority.
Next let's examine the word transliterated in English as vain. It is in the Hebrew shav' which is to say ruinous or useless.
As such we are not to trivialize God by using his position in a useless or callous way. Why?
Job 35:13 "Surely God will not hear vanity, neither will the Almighty regard it."If we dishonor God's authority, his response is to ignore us. He quits taking what we say to heart because those who use his name in vain dishonor him.
When I cautioned a person who used the popular slang "Oh my God", the response was "I meant nothing by it!" Although that person perceived herself as innocent, in fact she was not. Saying that expression with even an acronym (OMG) or a substitute (My Word) is useless because no honor is given to God by it's use.
Even substitutions are vanity because God can read our minds:
Psalm 94:11 "The Lord knoweth the thoughts of man, that they are vanity."When we cover our sin of disrespect with substitute expressions, God is wise enough to know what we really meant in our hearts... nothing. To cover up what is intended is vanity. It's useless in the sight of God. We are to let our yes's be yes and our no's no. We need no divine expressions of amazement short of "glory" and "hallelujah"!
Even when we pray because of routine, God's authority is trivialized. What I mean is a prayer such as this is vanity: "Dear Lord, we thank you this day, God, for what we have, Lord, because we love you, Father, and pray for these things in Jesus name."
Therein, the words seem honorable, but if we think about the prayer, people use God's titles as commas, as pauses to think, and as a routine prayer. In effect the titles are in vain because the reverence may not be there.
Perhaps a better prayer would be: "My Father in heaven, hallowed is your name"... and so on because the Lord's prayer is to be our guide if it is said from the heart, and not done as a ritual. Many do that as even I sometimes do. Such rote prayers are useless unless they are not coming profoundly from the heart. When one prays "dear God" that person must truly hold God "dear" or the prayer is vanity:
Ecclesiastes 12:8 "Vanity of vanities, saith the preacher; all is vanity."When we refer to God without magnifying who he is, it is vanity and we are guilty of breaking a commandment. Why? We fail to obey his will and miss the mark set by God. We are to honor God and we are to do that with sincerity and obedience. Using his titles flippantly, carelessly or uselessly is sinful. Will we Christians go to hell for such callousness? Likely not, because God has grace, but surely he is disappointed that those who use his name in vain (carelessly) do so at their own peril in opposition to his will.
Of course we can pray in the onoma (Greek) of Jesus. Onoma being the "authority" of Jesus because Jesus is NOT God incarnate's name. He just IS because he IS God. He is merely called by the common name Lesous (Hebrew); (Matthew 1:21).
Neither should Jesus' name be used in vain because Jesus IS God. We can submit our payers to his authority as our mediator to God, but because Jesus is God, we are never to use his name carelessly.
With all that said, God is not a knit-picker. He doesn't pounce on our every careless thought, word nor deed because he realizes that we're merely humans. That's his grace and he will be merciful when the time comes. However, we should still honor and respect him for who he is to please him, just as we call Queen Elizabeth "Your Highness" out of respect for her worldly position.
Does she deserve that reverence? No, but God does!