From Eminem's book "Angry Blonde".

“While putting together my second album, I kind of wanted to come up with an “I Don’t Give a Fuck,” Part 3. Jeff from FBT was playing this acoustic guitar track. He then started singing the hook “Cause I’m just Marshall Mathers”. It’s ill, because every time we’re fucking around in the studio we seem to come up with the dopest shit. We’ll fuck around and be smiling while we’re saying shit and I’ll say “Yo that’s dope. I should use that.” When I thought of the chorus I felt that what I needed to talk about in the verses was just me and my opinions. So I touched on everything the newest trends in hip-hop (which I’m not really with), to ICP, to my mother, to my family members who don’t know me and always wanna come around. I wanted to just spit fire in each verse and have the soft-ass innocent chorus. I think it captures the whole “front porch” feel despite on the album’s cover. When I recorded this I decided to call the album The Marshall Mathers LP.”