Actuall, Lyrics by Kandi Burris and Tiny Harris (before she married T.I.), Rap by Lisa “Left Eye” Lopes.
But people were using the word scrub long before the song. We were calling people scrubs when I was a kid; from someone who thought they had some type of athletic prowess but really had no game to some one who was fronting pretending to be something they weren’t ( and this was probably before the song writers were born)