Wormtail
From UnknowableWiki
Wormtail is the nickname of Peter Pettigrew, one of the four Marauders. It was given to him at Hogwarts by his three best friends due to the fact that his Animagus form is a rat (PA18).
James Potter refers to Peter as "Wormtail" after their Defence Against the Dark Arts OWL, as does Sirius (OP28). Sirius continues to do so after Hogwarts (OP5).
Lord Voldemort (GF1, GF29, GF33, DH1) and the Death Eaters (GF35, HBP2, DH23) always refer to Pettigrew as Wormtail. Harry often thinks of him and refers to him as such (PA21, GF2, GF10, GF14, GF17, GF29, GF30, GF32, GF33, GF34, GF35, GF36, OP9, OP28, DH23, DH24), as does Dumbledore (GF35).
The Marauder's Map is signed with the four Marauders' nicknames:
When the Map communicates with people who do not know the password to open it, statements by all four Marauders appear on the blank parchment; each of them is signed by one of them. Severus Snape attempts to force the Map to reveal its secrets to him after apprehending it one night; Mr. Wormtail recommends that Severus should wash his hair (PA14).
Fred and George Weasley, who find the Map in their first year at school, fondly refer to the its creators—whose real names they do not know—with gratitude, feeling that they owe much of their success to the Map (PA10, PA13).
