Most of the time we figure this commandment refers to cussing and damning.
However, in ancient times this referred to something similar to "Stolen Valor", claiming to be something that one was not.
"Name" meant family. Remember back to the parable of the Prodigal Son, one of the first things the father of the returning son does is to slip a ring onto the son's finger. That ring was used to seal documents. It was pressed into hot wax and was the equivalent of a signature.
The father was telling his son that he was being welcomed back as a full member of the family, as one who could carry the family name and thereby had the authority to enter into contracts on the family's behalf. The (formerly) prodigal son could commit the entire family to binding contracts that the entire family was obliged to fulfill.
From this perspective, taking the Lord's name in vain would mean that we claim to be followers of God or we claim to be Christians when we are something less than that.
How many people do you know who claim to be Christians but consistently fail to act in a Christian manner? How many people do you know who are "Christian, buts". That is, "I am a Christian, but my church is wrong about (insert long list here)" Some people call them a la carte Christians.
In those cases, they might assiduously avoid saying "God Damn!" and still be guilty of using God's "name" in vain.