If someone knocks on your Door they may use the rat-tat-ta-tat-tat… tat-tat Knock. But why? Where does this infamous knock that everyone seems to know come from?

This video explains the possible origins of that Door Knock, and seeks to explain why it has caught on so easily around the world.

No one quite knows when and where it first cropped up, but most agree that a song called “Shave and a Haircut – Shampoo” moved it into the mainstream.

And now almost everyone knows that simple beat, and many use it as their default door knock. Even though it’s very annoying.