"You shall not take the name of the Lord your God in vain, for the Lord will not leave him unpunished who takes His name in vain," (Exodus 20:7).
God commands us to use his name properly.
To take the Lord's name in vain means to use it in a manner that is not reverent. The phrase "the Lord's name" includes words such as "God," "Lord," "Jesus," and "Christ." These words are never to be used in any form of exclamation, swearing, or disrespect such as "Oh my ***." They are always and only supposed to be used in a manner that glorifies God.
Secular society has perfected using God's name in vain in movies and TV. It is so common to say "Oh my ***" in the entertainment media that Christians can easily become calloused and indifferent to the blatant violation of God's word in this regard. Christians are not to use any phrase or expression of the name of God that does not show honor and respect to God.