what is the meaning of taking the lord's name in vain
Thou shalt not take the name of the Lord thy God in vain It is a prohibition of blasphemy, specifically, the misuse or "taking in vain" of the name of the God of Israel, or using His name to commit evil. Exodus 20:7 reads:
Names of God in Judaism Rabbinic Judaism describes seven names which are so holy that, once written, should not be erased: The Tetragrammaton (whether written YHWH or Adonai), El ("God"), Eloah ("God"), Elohim ("Gods"), Shaddai ("God Almighty"), Ehyeh, and Tzevaot ("[of] Hosts").[1] Other names are considered mere epithets or titles reflecting different aspects of God,[2] but chumrah sometimes dictates special care such as the writing of "G-d" instead of "God" in English or saying Ṭēt-Vav (טו, lit. "9-6") instead of Yōd-Hē (יה, lit. "10-5" but also "Jah") for the number fifteen in Hebrew.[3]