Touch wood - British English
Knock on wood - American English
This expression is said in order to avoid bad luck, either when you mention good luck that you have had in the past or when you mention hopes you have for the future. The expression is usually used in the hope that a good thing will continue to occur after it has been acknowledged.
"I have never broken my leg, touch wood." - I have never broken one of my legs and I hope that, with good luck, I never will.
"I was sick all of last week, but I think that I'm over it now, touch wood." - I'm hoping that I will continue to be better after being sick.
Touch wood is an example of a superstition: something that we do in order to have good luck. It is not based on human reason or scientific knowledge, but is connected with old ideas about magic and the supernatural.
It is commonly thought that touching wood has been a superstitious action to prevent evil throughout history.
Many languages and cultures have a similar superstition. Do you 'touch wood' in your country? What do you do to keep your good luck?