Niagara Falls is not only one of the famous waterfalls in the world but also the largest waterfall in the US in terms of volume. It is comprised of three different waterfalls - Horseshoe Falls, American Falls, and Bridal Veil Falls.
Frankly, this superstition is pretty practical. Who wants to be responsible for stumbling and knocking a carpenter off his perch?
This superstition arises from old beliefs in witches and their animal familiars, which were often said to take the form of domestic animals like cats.
Remember confirmation bias? The belief that bad luck comes in threes is a classic example. A couple of things go wrong, and believers may start to look for the next bit of bad luck.
The fixation on wood may come from old myths about good spirits in trees or from an association with the Christian cross. Similar phrases abound in multiple languages
The story goes that two people used to cross index fingers when making a wish, a symbol of support from a friend to the person making the wish.
And not just because you'll poke someone's eye out. Opening an umbrella indoors is supposed to bring bad luck, though the origins of this belief are murky.
If you're not scared of Friday the 13th, you should be scared of the word used to describe those who are: friggatriskaidekaphobics. (An alternative, though just as tongue-twisty, word for the fear is "paraskevidekatriaphobia.")