Cause I was...
What is the origin of the custom of knocking on wood for luck?
A few possibilities are repeated fairly consistently in the search results for our query "knock on wood origin."
The explanation we prefer is the ancient belief that spirits either dwelled in or guarded trees. We prefer this because many cultures around the world show evidence of tree worship dating back thousands of years.
Greeks worshipped the oak as it was sacred to Zeus, Celts believed in tree spirits, and both believed touching sacred trees would bring good fortune. Irish lore holds that "touching wood" is a way to thank the leprechauns for a bit of luck. Pagans also held similar beliefs of protective tree spirits. Chinese and Koreans thought the spirits of mothers who died in childbirth remained in nearby trees.
Another explanation points to the wooden Christian cross as the origin of "good luck," although this is likely a Christian adaptation of earlier pagan practices.
A Jewish version traces the origin to the Spanish Inquisition of the 15th century. At the time, persecuted Jews fled to synagogues built of wood, and they devised a coded knock to gain admission. Since this practice spared countless lives, it became common to "knock on wood" for good luck.
So there you go...