Invented by Blagdon Blay sometime in the early 17th century. His house had been broken into nineteen times through use of the Unlocking Charm (Alohomora), and so he invented this spell to counteract it.
Behind the scenes
- It is possible that Filius Flitwick placed this charm onto the third obstacle of the chambers that lead to the Philosopher's Stone, as the door there cannot be opened with the Unlocking Charm.
- Harry Potter suspected that Dolores Umbridge, then Defence Against the Dark Arts professor, locked her office to prevent the Unlocking Charm from working, possibly referring to this charm.