The Hebrew shav (also shaw) denotes emptiness, vanity, or falsehood. It appears in the third commandment ('You shall not take the name of the LORD your God in shav' — in vain/emptiness) and in Psalm 24:4 ('who does not lift up his soul to an idol or swear by what is false [shav]'). The word encompasses both moral emptiness (hollow promises, false oaths) and ontological emptiness (idols that have no real existence).
The prohibition against using God's name in shav (Exodus 20:7) is not simply about profanity but about the deeper sin of treating the Most Real Being as though He were unreal — invoking His name without weight, reverence, or truth. Shav is the antithesis of emet (H571, truth) and amen (H539, faithful). Idolatry is fundamentally the worship of shav — nothingness dressed up as something. The New Testament counterpart is mataios (G3152, vain/empty) — Paul warns believers not to return to mataia (vain things) after knowing the living God.