|The subject of this article has no official name.|
It is a fan-given name as substitute for lack thereof, and should not be considered as part of the Attack on Titan universe.
Before the fall of Wall Maria, Armin's grandfather possessed a book containing illegal information about the world beyond the Walls. He gave this book to his grandson, Armin Arlert, who showed it to his best friend Eren, kindling his desire to see the outside world.
During his intimidation, or "rite of passage," from Keith Shadis, Armin states his name and is insulted by the instructor for it. When Shadis asks him if his parents gave him the name Armin replies that it was given to him by his grandfather.