take someone's name in vain

Speak casually or idly of someone, as in There he goes, taking my name in vain again. This idiom originated as a translation from the Latin of the Vulgate Bible (Exodus 20:7), "to take God's name in vain," and for a time was used only to denote blasphemy and profanity. In the early 1700s it began to be used more loosely as well.