What does the phrase “knock on wood” mean?
The origin of the expression is almost certainly connected with a religious belief or superstition, but the exact nature of the belief or superstition is unknown. It may derive from an ancient pagan belief that knocking on a tree was a way to ward off evil spirits, or to call upon protective spirits who supposedly lived in certain trees, especially the oak. Another possible connection is the Christian ritual of touching a wooden crucifix when taking an oath or praying for good fortune. The early Christians may have thought they were touching part of the genuine cross used in the Crucifixion. Later it was thought that touching any wooden crucifix, or part of a crucifix, would confer the same benefits, as would touching any piece of wood that once was part of a sacred tree.
