TAKE ONE'S NAME IN VAIN

{v. phr.} 1. To call upon (God) as a witness to your truth or honesty when you are lying; swear by (God) untruthfully. * /You shall not take the name of the Lord your God in vain./ 2. {informal} To talk about a person or mention his name. * /"Did I hear someone taking my name in vain?" asked Bill as he joined his friends./