"Bass player Krist Novoselic remembers Cobain writing "Polly" after reading a newspaper article about the abduction, torture and rape in June 1987 of a 14-year-old girl by Gerald Arthur Friend; Friend had picked her up near the Tacoma Dome in his car after she had attended a rock concert. She was able to earn his trust and sympathy by convincing him she enjoyed it. She managed to escape when he stopped for gas. She got out of the vehicle and made a scene attracting attention from surrounding people.
Dating back to at least 1988, "Polly" stands alongside "About a Girl" as one of singer/guitarist Kurt Cobain's earliest forays into unfiltered pop songwriting. It was originally titled "Hitchhiker", and later "Cracker", but was renamed "Polly" sometime in 1989. It was left off Nirvana's 1989 debut album, Bleach, because Cobain believed it was not consistent with the band's heavy grunge sound of the time." [wikipedia]