How did Black Sabbath get their name?

Formed in 1968 as the Polka Tulk Blues Band, a blues rock band, and name taken either from a brand of talcum powder or an Indian/Pakistani clothing shop, the group went through line up changes. After shortening the name to Polka Tulk, the band again changed their name to Earth (which Osbourne hated), broke up and reformed.

While playing shows in England in 1969, the band discovered they were being mistaken for another English group named Earth, so they decided to change their name again. A cinema across the street from the band's rehearsal room was showing the 1963 horror film Black Sabbath starring Boris Karloff and directed by Mario Bava. 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 and Butler wrote the lyrics for a song called "Black Sabbath", which was inspired by the work of horror and adventure-story writer Dennis Wheatley, along with a vision that Butler had of a black silhouetted 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. 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.