Many languages have expressions of anger or dismay that include the word "God". In addition, many times people "swear to God" to try to convince others they are telling the truth. Another offense might be to say that "God told me" to do something when He didn't. The actual name of God in the Old Testament was YHWH, sometimes pronounced Yahweh or Jehovah. Pious Jews refrain from using this name or even the word God, for which they substitute G_d. This is to avoid using God's name in a way that might break this commandment.