The padlock originated from Egypt and Babylon before spreading to the rest of the world. It is used to restrict access to buildings, personal property like suitcases, and many other places. The padlock is a sign of access denial; remember “under lock and key?”
The padlock is not just an innovation; it is a sign of death of trust. Growing up in the countryside, we had no padlocks. We just latched the doors and that was enough. I used my first padlock when I came to school in the city.