'Name of the Lord' in the Bible

‘You shall not take the name of the Lord your God in vain [that is, irreverently, in false affirmations or in ways that impugn the character of God]; for the Lord will not hold guiltless nor leave unpunished the one who takes His name in vain [disregarding its reverence and its power].

When a prophet speaks in the name of the Lord and the thing does not happen or come true, that is the thing which the Lord has not spoken. The prophet has spoken it presumptuously; you shall not be afraid of him.