The old superstition of knocking on or touching wood to ensure continued good health or fortune remains common today. One often hears the expression used after someone has stated something like, "I've never had a toothache," then quickly adds, "knock on wood." Many authorities on folklore and traditions believe that the custom may have originated in the practice of touching wood upon every occasion of happiness or good fortune in gratitude and veneration to Christ who died upon a wooden cross.
Others state that their research indicates that the ancient Druids of Great Britain and Northern Europe began the practice with their belief that the trees housed deities. Touching the trees in a respectful manner encouraged the gods and goddesses within to grant one's physical selves health and prosperity and one's spirit eternal life. Through the process of cultural evolution within the mass consciousness, the custom of touching or knocking on wood came to be looked upon as a means of warding off ill luck.