Why do we say "knock on wood"?

Answer 1

The origin of the expression is almost certainly connected with a religious belief or superstition, but the exact nature of the belief or superstition is unknown. It may derive from an ancient pagan belief that knocking on a tree was a way to ward off evil spirits, or to call upon protective spirits who supposedly lived in certain trees, especially the oak. Another possible connection is the Christian ritual of touching a wooden crucifix when taking an oath or praying for good fortune. The early Christians may have thought they were touching part of the genuine cross used in the Crucifixion. Later it was thought that touching any wooden crucifix, or part of a crucifix, would confer the same benefits, as would touching any piece of wood that once was part of a sacred tree.

source: http://www.randomhouse.com/wotd/index.pperl?date=20010918

Answer 2

[Q] From Mike Gast: “What is the origin and true meaning of knock on wood or touch wood?”

[A] To touch wood or knock on wood is a superstition action to ward off any evil consequences or bad luck, perhaps because of some recent action you’ve taken or untimely boasting about your good fortune (“I’ve never been in danger of drowning, touch wood”); it can also be a charm to bring good luck.

The origin is unknown, though some writers have pointed to pre-Christian rituals involving the spirits of sacred trees such as the oak, ash, holly or hawthorn. There is, I’m told, an old Irish belief that you should knock on wood to let the little people know that you are thanking them for a bit of good luck. There’s also a belief that the knocking sound prevents the Devil from hearing your unwise comments. Others have sought a meaning in which the wood symbolises the timber of the cross, but this may be a Christianisation of an older ritual. It wasn’t always wood that was lucky: in older days, iron was also thought to have magical properties, and to touch iron was an equivalent preventative against ill-fortune.

The phrase itself is relatively modern, as the oldest citation for the British version of the phrase, touch wood, that I can find dates only from 1899. The American equivalent knock on wood is roughly contemporary, with my first example from 1905.

Answer 3

I have it earlier: 1871, 1888
Another few references to an ancient Greek practice.

Interesting but i would not do it a religious Christian school,
they will rap your knuc's with that medal edged ruler the good Sisters used to carry.



Q] “What is the origin and true meaning of knock on wood or touch wood?”

[A] To touch wood or knock on wood is a superstition action to ward off any evil consequences or bad luck, perhaps because of some recent action you’ve taken or untimely boasting about your good fortune (“I’ve never been in danger of drowning, touch wood”); it can also be a charm to bring good luck.

The origin is unknown, though some writers have pointed to pre-Christian rituals involving the spirits of sacred trees such as the oak, ash, holly or hawthorn. There is, I’m told, an old Irish belief that you should knock on wood to let the little people know that you are thanking them for a bit of good luck. There’s also a belief that the knocking sound prevents the Devil from hearing your unwise comments. Others have sought a meaning in which the wood symbolises the timber of the cross, but this may be a Christianisation of an older ritual. It wasn’t always wood that was lucky: in older days, iron was also thought to have magical properties, and to touch iron was an equivalent preventative against ill-fortune.

The phrase itself is relatively modern, as the oldest citation for the British version of the phrase, touch wood, that I can find dates only from 1899. The American equivalent knock on wood is roughly contemporary, with my first example from 1905.

AND:Why do people knock on wood? Knocking or rapping on wood to ward off punishment
for boasting is one of the most prevalent of all superstitions. ...

Answer 4

I've said it since I was a kid. But some people really believe it is a protection against 'bad' when you say it. Example: "I've never been in a car wreck, knock on wood!" Then they literally knock on wood hoping/believing they will NOT ever have a car wreck.

Answer 5

It's an old superstition that there used to be good spirits who live in the trees, if something bad happened, you would 'knock on wood' for good luck or protection.

Answer 6

Greeks worshipped the oak as it was sacred to Zeus, Celts believed in tree spirits, and both believed touching sacred trees would bring good fortune. Irish lore holds that "touching wood" is a way to thank the leprechauns for a bit of luck. Pagans also held similar beliefs of protective tree spirits. Chinese and Koreans thought the spirits of mothers who died in childbirth remained in nearby trees.

Another explanation points to the wooden Christian cross as the origin of "good luck," although this is likely a Christian adaptation of earlier pagan practices.

A Jewish version traces the origin to the Spanish Inquisition

Answer 7

I think it was the Greeks who thought some gods lived in trees.
They actually would knock on the tree before expressing the request. They did this to arouse the "deity" within in hopes of
an answer to their request (prayer).

Answer 8

because wood is very knockable! for instance you cannot "knock on marshmallows".