The phrase 'knock on wood' is believed to be Germanic in origin. In history it was believed that tiny but lucky creatures lived in the wood. Knocking on the wood would bring them out to gran you good luck.
The exact origin of the phrase "knock on wood" is unknown, however many speculate that is could have come from rituals in early times where trees were considered sacred spirits. Others believe the phrase originated in Ireland. To knock on wood was to alert leprechauns that you were thanking them for giving you good luck. Another popular belief is that by knocking on wood you prevent the devil from hearing what you have just said, which in turn prevents the action from occurring. It is also possible that the origination of the phrase "knock on wood" is derived from Christianity and the wood is a reference to the cross on which Jesus was crucified.The British version of this expression, 'touch wood,' is supposed to have derived from a 17th century practice of warding off bad luck by touching something made of wood while saying 'absit, omen!'Phrase maven Gary Martin (please see link) says it became 'knock on wood' in the United States by the early 20th century.
"Kingdom Come" is a phrase from the bible, specifically: "...Kingdom Come, Your Will Be Done, On Earth as it is in Heaven...." The literal meaning being "I will knock you to heaven" but the social meaning of "I will hurt you greatly"
The door (don't knock it until you have tried (opening) it !
It was believed that trees had spirits and to invoke those spirits you would tap on the tree, "knock on wood". The practice tended to be a way to ask the spirits to intervene and save you from a bad out come (bad luck). This is why when you say something you do not want to come about you "knock on wood."
Knock on wood means you are hoping that it happens.
All my children are healthy, knock on wood.
Knock on wood means you are hoping that it happens.
Touch or knock on wood is an old superstition based on the belief that spirits resided in trees and plants. You touch wood (some people say knock on wood) to ask for good luck or the spirit's blessings.
The phrase "knock it off" meaning to tell someone to stop doing something originated from an auction setting. Traditionally, "knock it off" is a request that is given to an auctioneer to end the bidding. This refers to the auctioneer "knocking his gavel," a sign to close bidding.
Knock on Wood - Eddie Floyd album - was created in 1967.
Knock on Wood - 1998 was released on: USA: 1998 (Dances With Films Festival)
If you mean pumpkins or something for decoration, then I would say because they enjoy doing that.