superstition: knock on wood To knock on wood or touch wood is a way to ward of evil or bad consequences. The origins are unknown, although the Irish are believe to have started this. As they would knock, or touch oak to thank the little people for the good luck you have been having. Other cultures believe the knocking would drowned out what you have said so that the evil spirits wouldn't have heard what you said. Early Christians did this because they believe wood symbolized the cross. Others believe this to be from a game kids played in the early 1800's called Tiggy Touch Wood. In the game you could not be tagged if you were touching wood. If no wood is available some people will knock on their head.