The Collaborative International Dictionary
To take the name of God in vain
Vain \Vain\, n. Vanity; emptiness; -- now used only in the phrase in vain.
For vain. See In vain. [Obs.]
--Shak.
In vain, to no purpose; without effect; ineffectually. ``
In vain doth valor bleed.''
--Milton. `` In vain they do
worship me.''
--Matt. xv. 9.
To take the name of God in vain, to use the name of God with levity or profaneness.