History (Formation and early days (1968–1969))

Following the breakup of their previous band Mythology in 1968, guitarist Tony Iommi and drummer Bill Ward sought to form a heavy blues band in Aston, Birmingham. The two enlisted bassist Geezer Butler and vocalist Ozzy Osbourne, who had played together in a band called Rare Breed, Osbourne having placed an advertisement in a local music shop: "Ozzy Zig Needs Gig- has own PA". The new group was initially named The Polka Tulk Blues Band (after a cheap brand of talcum powder Osbourne saw in his mother's bathroom) and also featured slide guitarist Jimmy Phillips and saxophonist Alan "Aker" Clarke. After shortening the name to Polka Tulk, the band changed their name to Earth (which Osbourne hated) and continued as a four-piece without Phillips and Clarke. While the band was performing under the Earth title, they recorded several demos written by Norman Haines such as "The Rebel", "Song for Jim", and "When I Came Down". In December 1968, Iommi abruptly left Earth to join Jethro Tull. Although his stint with the band would be short-lived, Iommi made an appearance with Jethro Tull on the The Rolling Stones Rock and Roll Circus TV show. Unsatisfied with the direction of Jethro Tull, Iommi returned to Earth in January 1969. "It just wasn't right, so I left", Iommi said. "At first I thought Tull were great, but I didn't much go for having a leader in the band, which was Ian Anderson's way. When I came back from Tull, I came back with a new attitude altogether. They taught me that to get on you got to work for it."

While playing shows in England in 1969, the band discovered they were being mistaken for another English group named Earth, and decided to change their name again. A movie theatre across the street from the band's rehearsal room was showing the 1963 Boris Karloff horror film Black Sabbath. While watching people line up to see the film, Butler noted that it was "strange that people spend so much money to see scary movies". Following that, Osbourne wrote the lyrics for a song called "Black Sabbath," which was inspired by the work of occult writer Dennis Wheatley, along with a vision that Butler had of a black silouetted figure standing at the foot of his bed. Making use of the musical tritone, also known as "The Devil's Interval", the song's ominous sound and dark lyrics pushed the band in a darker direction, a stark contrast to the popular music of the late 1960s, which was dominated by flower power, folk music, and hippie culture. Inspired by the new sound, the band changed their name to Black Sabbath in August 1969, and made the decision to focus on writing similar material, in an attempt to create the musical equivalent of horror films.