Knock on wood is a superstitious phrase spoken when one has acknowledged some good fortune and wishes the good fortune to continue. The idea is that an admission of good fortune may arouse the jealousy of a mischievous spirit who will destroy the person’s good luck. In pagan times, trees were believed to be the homes of woodland spirits. Knock on wood is an American phrase that appears around the beginning of the twentieth century.
Touch wood is a superstitious phrase spoken when one has acknowledged some good fortune and wishes the good fortune to continue. Touch wood is the British counterpart to the American knock on wood. Touch wood dates at least from the early seventeenth century, and perhaps earlier. Often, when a superstitious person knocks on wood or touches wood, he jocularly taps his head. Related phrases are knocks on wood, knocked on wood, knocking on wood, touches wood, touched wood, touching wood.
Examples
“Knock on wood, we haven’t had any exposure in over a year,” said Koharski, who lives in Ashburn, Va. (The Washington Post)
No matter how silly they may sound, the idea that simply buying a certain shirt, knocking on wood or throwing salt over a shoulder could help control things out of most student’s hands is quite appealing. (The St. Louis Jewish Light)
So, knock on wood, we’ve been able to put out pretty good shows almost every Friday. (The International Business Times)
“Knock on wood Netflix would even want to do a second season, but I wouldn’t be able to jump in the writers’ room and start writing.” (USA Today)
“Touch wood wouldn’t that be amazing to still be doing this in our 50s?” (The Mirror)
“I’m sure I would do it again if I had to, but touch wood that never happens.” (The Aberdeen Press & Journal)
A Diocese of Chichester spokesman told The Argus they hoped House’s conviction would “touch wood” be the last case to come to light. (The Argus)