Expression idiomatique en anglais: knock on wood or touch wood

• Tap knuckle on wood in order to avoid bad luck
• Said when you want good luck or a good situation to continue
• Said when expressing hope for something to occur

• I am expecting a promotion and a big pay hike this year, touch wood.
• The team I support has been winning every game so far, knock on wood.
• We have had a great week so far and, touch wood, we will end it on a high note.
• We expect to close the deal by the end of this week, knock on wood.
• We have had a smooth journey so far, touch wood.
• Our new venture has got off to a great start and touch wood, we’ll be doing good business by the end of the year.
• Your health seems to be improving, knock on wood.

The phrase originates based on a superstition that knocking or touching wood will ward off evil spirits. Wood and trees have an association with good spirits in mythology. It was considered good luck to tap trees to let the good spirits know that you were there. The British version of the phrase is « touch wood », while the American version is « knock on wood ». The phrase originated in latin in the early 17th century, and came into English (British version touch wood) by 1850. The American version knock on wood was known from the early 20th century.

Source: http://idioms.in/knock-on-wood/