Thou shalt not take the name of the Lord thy God in vain; for the Lord will not hold him guiltless that taketh his name in vain. Exodus 20:7
What does it mean to take the name of the Lord thy God in vain? The Hebrew word translated as vain means vain, empty, and deceitful and can also mean destruction. Both meanings are translated as vanity in Job 15:31:
Let not him that is deceived trust in vanity: for vanity shall be his recompense.
In other words, vanity, emptiness, and deceit lead to destruction.
This word in Hebrew is derived from a root verb meaning to rush over as in a storm that destroys and lays waste. Both linguistically and in reality there is a profound link in the association between vanity, emptiness, and deceit on the one hand and destruction on the other that suggests they are one, and as such, returning to the third commandment, another way to look at the first phrase is: Thou shalt not take the name of the Lord thy God to destroy;
There is ample historical precedence for this interpretation, and viewing the commandment from this perspective is instructive as to exactly what the commandment prohibits and the gravity of the sin involved. One such precedent is Nimrod, whose name means rebellion and also valiant, who becomes a mighty hunter before the Lord (Genesis 10:9). The Hebrew word translated here as before is face, and the literal meaning is that Nimrod is in the face of the Lord, perhaps that he associates with the Lord at some point, or not necessarily mutually exclusively that he is between the Lord and others, causing confusion as to who is the source of authority and power, who is the source of salvation. As his name suggests it may mean that he comes out at some point in complete rebellion against God and sets himself up as a counterfeit savior, or a false seraph, as did the serpent in the Garden of Eden.
One myth regarding Nimrod (detailed in The Legends of the Jews, Ginzberg, Volume I 177-178) is that due to his possession of the garments given to Adam in the Garden of Eden, which make him both irresistible and invincible, he becomes a mighty hunter having great power over wild beasts, thus acting as a protector of men, gaining their confidence and allegiance, and thereby becoming their ruler. In this way, he also becomes a mighty hunter of men, a conqueror, and oppressor, a man after the manner of pre-flood men who are the mighty men that were of old, the men of renown. (Genesis 6:4) As the beginning of his kingdom is Babel (see Genesis 10:10) Nimrod represents false salvation in the construction of the tower and city of Babel, and this through force and oppression of its inhabitants.
From the very few verses mentioning Nimrod together with the myths regarding him he emerges as a striking type of Satan—he at some point may associate with the Lord and represent him either legitimately or as counterfeit; he is mighty, possibly even to a miraculous point and makes for himself a great name; he provides a counterfeit salvation to others; the salvation he provides is appearance based and illusory; he saves through oppression and enslavement to the point where the salvation he provides is ironically identical to the enslavement and destruction; while God is the Word and truth, Nimrod more than any other man is central to the devolution of language and spreading of lies...
Nimrod, and Satan before him, typify to an instructive extreme what the third commandment prohibits, the gravity of the sin involved, and the destructive consequences that come from disobeying this commandment—it is to associate with God in appearance for the purpose of representing or counterfeiting Him in order to do what is contrary to His will and ultimately destructive to His children.