This is one of the passwords that was not immediately obvious. It may take a few different endings to be completed before you make the connection. The clue for this are the mothers memento’s. These items belong to 2 of the girls in the game. If you need a further clue for the mothers memento’s to unlock force quit box D, keep an eye out for 2 items that are made of metal that both girls keep on them as a memory of their mothers.
If you are still having trouble with this, you need to find the brooch and the bird cage. It can be a bit confusing here as the brooch has writing on it that may throw you off. The passwords are for the items themselves.