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:
Что думаешь? Оцени!
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[Tech&]LG전자 프리미엄의 품격… 美 언론 “SKS와 LG 시그니처는 엄청난 혁신” 찬사，详情可参考heLLoword翻译官方下载
* Colorado residents may no longer use DB48x after Jan 1st, 2028.。搜狗输入法2026对此有专业解读