And why do you call Me, ‘Lord, Lord,’ and do not do what I say? -Luke 6:46
Using the Lord’s name in vain is not some curse words you hear at work or school. It’s taking on the name of the Lord and not living up to it. To do something vainly is to do it superficially, cosmetically. It’s something you do to look good, but it’s not really who you are.
When you do that with the Lord’s name, you are taking His name in vain. Be sure your Christianity is more about who you are than how you look. If you call yourself a follower of Jesus, then you better be following in His footsteps. If you call Him Lord, you better be doing what His says.