Where and when did the superstition "knock-on-wood" originate?

Answer 1

Hmmm.. interesting. I never knew this before.. never will I knock three times again. ;)

Answer 2

It is commonly thought that knocking on wood has been a superstitious action to ward off evil throughout history. Some believe it has to do with knocking on the wooden cross. Another explanation for this practice is the pagan belief that spirits (dryads) lived in trees. By knocking on the wood of a tree while making some sort of a bold statement, the speaker could prevent the spirit from hearing him and stop the spirit from interfering.

Answer 3

In ancient Ireland it was the belief that three knocks at the door meant that death would befall someone in the home, so the habit of two knocks on the door became significant as good luck. To this day people knock on wood for good luck, but you should only knock twice!

Answer 4

It originated in the belief that spirits lived in trees, and that those spirits could hear your conversations, and could sometimes do you mischief, because they wanted to be noticed.
So if you said you hoped or expected a certain good thing to happen, you didn't want a tree spirit to make mischief in light of what you have just said, so you knock on wood (originally a tree) to acknowledge their presence, that way they didn't have to get your attention by spoiling your hopes.

Answer 5

According to Steve Roud, the earliest documented references to "touching wood" are from 1805 and 1828 and concern chasing games like "Tiggy-touch-wood", where you are safe from being "tagged" if you "touch wood". Says Roud, "'Tiggy-touch-wood' was an extremely well-known game, and it is most likely that the phrase passed into everyday language."

Answer 6

Trees used to have a special significance. ie. oak , ash, hazelwood.
It was tapped to see if it was sound, and not riddled with termites.