Actually I think I got it for free in the giveaway bin outside of McKay's (a store where you can turn in your old CDs, Books, Video Games & DVDs for $$$ or store credit). It's called "Panati's Extraordinary Origins of Everyday Things" by Charles Panati.
I intended to use it for a weekly post "jump off" point, kind of like CardioGirl's Question of the Week. (I keep stealing crap from her blog. She should take it as a compliment.☺)
So here's the first installment of Did you know?
The origin of the "Knock Wood for good luck" superstition began in 2000 B.C. in North America by the American Indians.
The Native Americans believed that boasting of a future event (like winning a battle or a great harvest, for example) basically insured that it wouldn't happen. In order to negate the "bad juju", they touched the bark of an Oak Tree.
The Oak Tree was chosen because, apparently, the oak tree was most often the tree struck by lightning and they assumed that the Sky God lived there so they appeased him for bragging by knocking on -
This is how you can tell that I live with a 14 year old. I was about to say "by knocking on his wood" but I could hear Evan in my head saying "Heh heh, you said 'his wood'"
Whatever, now you know where the superstition came from.