take someone's name in vain

== English == === Etymology === By extension from the widely known religious proscription against taking the Lord's name in vain, that is, uttering it in ways that are gratuitous and irreverent, such as swearing oaths casually. === Verb === take someone's name in vain (third-person singular simple present takes someone's name in vain, present participle taking someone's name in vain, simple past took someone's name in vain, past participle taken someone's name in vain) To speak insultingly about someone, especially behind their back.