Why Do We ‘Knock on Wood’?

Someone who is superstitious may physically knock on wood — or simply say the phrase — as a way to ward off misfortune. While the precise expression “knock on wood” is an Americanism dating to the early 20th century, the origin of the concept is debated. There are theoretical ties to some ancient pagan and Christian beliefs, which gave rise to a similar phrase used in 19th-century Britain.

Some theorize the connection between wood and good fortune originated within ancient pagan cultures that believed good spirits resided in trees, and knocking on a tree trunk was a way to awaken those spirits and ask for protection. Others point to Christianity and the wooden cross on which Jesus was crucified; they theorize that knocking on wood is meant to request his protection. 

But still others deride both of these theories as unlikely. Authors Jacqueline Simpson and Stephen Roud are particularly critical of any ancient theories, saying the belief is a more modern invention. In A Dictionary of English Folklore, published in 2000, they write about a 19th-century children’s game called “tig-touch-wood,” in which touching wood provided players protection from being chased or tagged.

Though the origins of this concept can be argued, we know that the idiom “touch wood” became popular in England during the 19th century, when it was often said aloud without a physical action to accompany it. The phrase later showed up inAmerica in the early 20th century, when it was adapted to “knock on wood” (though the reason for this shift in verbiage is unclear). A different version is popular in Italy: There they say “touch iron,” which is derived from a regional belief that strong, fire-forged metal wards off evil spirits.