User blog comment:Hikaruyami-having fun*/Get To Know Them/@comment-3193128-20110709023504/@comment-3193128-20110709024724

2 things

1) "Killing Spree day" = when he and his family had to kill an entire neiborhood to stop being hunted for power

2) Lady from Limbo = 9's mother for being a powerful and power crazy witch so to insult her they came up with that nickname.