Bible Dictionary
VAIN
Vain means empty, futile, or without lasting value. To take God’s name in vain is to use His name for an empty or improper purpose rather than with reverence and truth.
Definition
Vain means empty, futile, or without lasting value. In modern English it can often be replaced by “empty,” though the phrase “in vain” may require an implied noun such as ways or purposes.
Biblical Usage
To take God’s name in vain means to take or use it for an empty or improper purpose. The expression is connected with the commandment against such misuse of God’s name.
Historical Background
The adjective represents the same Hebrew and Greek word groups as “vanity,” with New Testament forms meaning empty. Translation may use “empty” where that more clearly conveys the sense.
Historical Bible Dictionaries
International Standard Bible Encyclopedia (ISBE)
<p>van: The adjective of "vanity," and representing the same Hebrew and Greek words as does the latter, with a few additions (chiefly kenos, "empty," and its compounds in the New Testament). And "vain" can always be replaced by its synonym "empty," often with advantage in modern English (Job 15:2; 1Co 15:14, etc.). The exception is the phrase "in vain," and even there the interchange can be made if some (understood) noun such as "ways" be added. So "to take God's name in vain" (Ex 20:7; De 5:11) means simply to take it for an "empty" ("not good") purpose.</p>