How come we use this expression in all language?
The expression is used by people around the world accompanied by the touching of an item made from wood as a form of protection.
But why ?
How could wood protect us?
The origin is quite old (Persia, or Egypt), and remains closely linked to the religion of the people concerned: Touch wood amounted to get under the protection of Atar, the Persians god of the fire.
For the Egyptians, wood possessed a kind of beneficial magnetism. To touch it placed you under the protection of this energy.
Closer to us, the saying was used by Christians as a reminder of the crucifixion of Christ on the Cross . Touch wood then returned to a kind of prayer to be placed under its protection and to protect themselves against adversity.
But does it work?
Well....Fingers crossed !
