For some, just the mere mention of something going wrong ignites a near-instinctual need to knock on the nearest wooden surface. And with iterations of the practice cropping up around the world, knocking on wood (or "touching wood," as they say in the UK and Australia) is one of the most common superstitions. But why has it become many people's go-to good luck insurance? Like any good superstition, the exact origins of knocking on wood are lost to time, but there are a few commonly held theories about its roots. According to ancient Pagan beliefs, spirits and gods lived in trees, so it made perfect sense to knock on those trees when you wanted to summon their protection. Supposedly, the first knock was to get the gods' attention and the second knock was to say thank you. This way, not only did they cover all their bases, but they were polite about it, too. It's been said that, later on, Christians adopted this superstition from Pagans and, in turn, made it more about Jesus and less about woodland fairies. Touching any wooden surface was believed to be equivalent to touching the wood of the cross, and doing so was seen as a call for God's protection. Some Christians even carried pieces of wood with them just to be safe. Touching wood also became a significant superstition within Judaism during the Spanish Inquisition. Many Jewish people hid from the inquisitors in wooden synagogues and a specific knock was required for entry. Knocking on wood was soon associated with safety and survival, and so the practice lived on after the Inquisition. Across the board, it seems that knocking on wood has always been meant to call upon a higher power to keep people safe for a bit. And all of these potential origins are actually pretty consistent with how we view knocking on wood today: We may not go around hitting every bookshelf we see just because we want some luck — for the most part, we only knock on wood when we're worried we might have drummed up some negativity with something we said or did. Now, if you'll excuse us, we need to find a travel-sized piece of wood.