Passwords? In Histroy of Magic? How were passwords considered history? Or maybe they were going to learn about a certain event that involved passwords? They'd have to wait a while and see.

As for what she knew about passwords, Renesmee raised her hand politely and waited her turn. "Professor, passwords are words, combinations, numbers or even riddles that are used to keep rooms or objects away from people whom do not have knowledge of the password." Just like the Slytherins could not get into the Hufflepuff common room and visa versa.