The name, Nibbles, stems from a gang member character in West Side Story named "Nibbles." It may also have something to do with how the character is designed to resemble a rat.
Nezumi tells Jonouchi that three gang members ambushed him, beat him, and stole his yo-yo. Out of anger, Jonouchi asks Nezumi to lead him to the gangsters. Yugi and Jonouchi travel to Hirutani's abandoned warehouse, where scores of gang members ambush the two boys. Nezumi runs away when Yugi and Jonouchi manage to defeat the gang members, Yugi luring them onto the roof which he then punctures with his own yo-yo enough times that their weight sends them crashing through.