Funny how a phrase is thought to hold so much power, not only over us, but over fate itself. As if uttering these three simple words can keep the worst from happening. I know I fall into the magic of KoW when I am trying to catch a flight or get somewhere on time. Or during my college days, after a really hard final. One wonders how would have history played out if only these words were said.
But this isn't about Trix. This goes beyond that. Where did this phrase originate? Through some extensive research I found that 84% of people in the United States use the power of KoW.* With that many people using the phrase, how can one not but help think, "Where did this come from?"
Taken from Wikipedia
It is commonly thought that knocking on wood has been a superstitious action to ward off evil throughout history involving Pagan belief systems. The same reference claims that knocking on wood is also used in some form of Christianity, but in a different context, where the wood represents the cross. In an alternate explanation, the wood represents the rosary. 
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 or out of respect for the wood spirit, touching a tree indicated seeking protection from the particular spirit.
However historian Steve Roud finds no evidence in the British Isles for the earlier theories, suggesting that the superstitions have not been traced beyond children's games of tag of the early nineteenth century. According to 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 more than likely that the phrase was passed into everyday language.Well folks, its a sunny day outside and I am off to play some Tiggy-touch-wood with the pup.
*Percentage supplied by WRBS.** Critics argue that the WRBS does not gather its statistics properly. In fact most say that they simply pick a number out of a hat.
**White Russian Bullshit Society