For many years I misunderstood what "taking God's name in vain" actually meant. Using the name "Jesus Christ" (both or either), or "God" as an expletive or 'cuss' word was not actually the subject of one of the Ten Commandments.
Think about the phrase "take the name", then insert "on" so it reads "take on the name". Compare the traditional/Christian/Biblical institution of marriage, and the practice of the bride "taking on the name of" her new husband as they wed.
"Taking the Lord's name" was really about the people advertising to the world that they were "God's people who lived by God's law". To paraphrase, what God was saying is basically this: "Do not take on My name [call yourselves My children], then live like you belong to the Devil (or the world, or any of the other tribes or nations you see around you, who practice wickedness)."
It was/is about living out their/our profession. We call ourselves Christians...but to the world, do we live as Christians?
Of course the speech/language which exits our lips is a sign of what's inside ("out of the mouth the heart speaks" - Matthew 12:34, Luke 6:45), but it was/is about behaviour and how that aligns with profession.
We could therefore say that the colloquial term 'nominal Christian' might refer to those who take God's name in vain.
I have certainly been guilty of this on many occasions...as we have all been.
Does that help?
For a more in depth understanding, study the act, and importance, of naming in the Old Testament, especially naming a person. Yehoshua (Joshua), Yeshua (Jesus) and Jabez are cases in point. It was much more than a labeling mechanism, contrary to what our modern scientific world view would have us relegate it to.
Listen to the following podcast for a Scholar's take on this:
"What is God's Name? Feat. Dr. Michael Heiser".
And here is something that is quite mind bending, and dare I say difficult for atheists to explain, which kind of illustrates the importance God seems to place on names:
Genesis 5 genealogy.