I made a list of all the passwords used in Hogwarts:

Gryffindor House
Caput Draconis (Book 1)
Pig snout (Book 1)
Wattlebird (Book 2)
Fortuna Major (Book 3)
Oddsbodokins (Book 3)
Flibbertigibbet (Book 3)
Scurvy cur (Book 3)
Balderdash (Book 4)
Fairy lights (Book 4)
Banana fritters (Book 4)

Slytherin House
Pure-blood (Book 2)

Dumbledore's Office
Sherbert Lemon (Book 2)
Lemon drop (Book 2)
Cockroach Cluster (Book 4)

Prefect Bathroom
Pine fresh (Book 4)