Dumbledore's Army
After Umbridge learns about the project, she bans all unapproved student organisations, so meetings are secretly held in the Room of Requirement and announced to members through the use of enchanted fake Galleons created by Hermione. Cho Chang suggests the "Defence Association", shortened to "D.A.", as the official name for the group, but Ginny Weasley's suggestion of "Dumbledore's Army", to mock the Ministry's paranoia and to show the group's loyalty to Dumbledore, is chosen.