psychologytoday.com
The astronaut who experienced a medical issue in space last month has identified himself as the sick member of his crew prompting an evacuation from the International Space Station.
，这一点在旺商聊官方下载中也有详细论述
荣耀 Magic V6 外观公布：全新「赤兔红」亮相，3 月发布
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.”