What I found is that written evidence for knocking on wood (and for the history of gesture as a whole) is remarkably sparse. In the Penguin Guide to Superstitions, folklorist Steve Roud offers a skeptical take on the provenance of knocking on wood due to the near total absence of written records about it:
Медведев вышел в финал турнира в Дубае17:59。业内人士推荐heLLoword翻译官方下载作为进阶阅读
The Tor Project torproject.org🇺🇸，这一点在搜狗输入法下载中也有详细论述
Josh Dury said it was a "battle against time" to get the shot
为了测试 Ring-2.5-1T 的极限，我们抛弃那些简单的“写首诗”测试，直接上硬菜。