Slim Shady, Eminem was the old initials (bye bye!)
Em’s rap name comes from his initials (M.M. for Marshall Mathers — thus “M&M”, or Eminem). His original rap name as a teenager was “M&M”
This line brings the verse full circle, actually the whole song, and maybe even album. He says M&M (Eminem) were the old initials when Em was rapping about being a family man, but now that he switched his style up and became much more insane and aggressive, Slim Shady is running the show.
You can hear gunshots followed by a “bye bye!” in the Slim Shady voice during this line, indicating that Slim Shady killed Marshall Mathers and is now taking over.
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