People knocking on wood is a superstitious act. People think that they say something bad and then knock on wood, it will not happen to them.
If you mean pumpkins or something for decoration, then I would say because they enjoy doing that.
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.
People say "Know the score" and "Knock on wood." They begin with the letter K.
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.
you knock on wood because say you say something like iv never broken a bone in my life you would say knock on wood and knock on wood 3 times so you dont jinx your self and break a bone tomarow. The origin of "knock on wood" is a bit cloudy. It seems to trace back to the European idea of touching wood to ward off bad luck, or acknowledge good luck. The knocking probably stems from the idea of a knocking sound preventing the Devil from hearing unwise statements. The modern American usage began early in the 20th century. There isn't any specific thing to do (you don't have to knock specifically three times as cited above), but the act is common.
Knock on wood means you are hoping that it happens.
All my children are healthy, knock on wood.
they do it about once every 2.3435663456567345635 seconds!
That's a non-Jewish custom.
Knock on Wood - Eddie Floyd album - was created in 1967.