The “Knocking on Wood” Wikipedia page mentions Roud’s conclusion, and this claim of a 19th century origin has circulated online as the final say on the matter. If you go back to the original, though, Roud’s proposal actually ends on an ambivalent note: “Before this theory [of 19th century origins] can be finally accepted, however, an examination of the history of European forms of this custom would be advisable.”
Раскрыты подробности похищения ребенка в Смоленске09:27，更多细节参见同城约会
What could Ozzy Osbourne's Birmingham legacy be?，更多细节参见同城约会
Features in Bullets:
One thing that Nava has got me thinking about is the deep history of gesture. Gesture exists on the borderland between nature and nurture. Certain physical actions are so universal that they communicate effectively not just across human societies but across species: bared teeth, for instance. Other gestures encode more specific cultural patterns, but do so in a way that is more expansive than language.