Following the break-up of their previous band Mythology in 1968, guitarist Tony Iommi and drummer Bill Ward sought to form a heavy blues rock band in Aston, Birmingham. They 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, the name taken either from a brand of talcum powder or an Indian/Pakistani clothing shop; the exact origin is confused. The Polka Tulk Blues Band included slide guitarist Jimmy Phillips, a childhood friend of Osbourne's, and saxophonist Alan "Aker" Clarke. After shortening the name to Polka Tulk, the band again changed their name to Earth (which Osbourne hated) and continued as a four-piece without Phillips and Clarke. Iommi became concerned that Phillips and Clarke lacked the necessary dedication and were not taking the band seriously. Rather than asking them to leave, they instead decided to break up and then quietly reformed the band as a four-piece. 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". The demo titled "Song for Jim" was in reference to Jim Simpson. Jim Simpson was a manager for the bands Bakerloo Blues Line and Tea & Symphony, as well as being trumpet player for the group Locomotive. Simpson had recently started a new club named Henry's Blueshouse at The Crown Hotel in Birmingham and offered to let Earth play there after they agreed to waive the usual support band fee in return for free t-shirts. The audience response was positive and Simpson agreed to manage Earth.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 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. 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, which was dominated by flower power, folk music, and hippie culture. Judas Priest frontman Rob Halford has called the track "probably the most evil song ever written". 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.

Question: What is the name of the band that was being mistaken for another band called "Earth"?
Answer: Black Sabbath

Question: When did the band come up with the name Black Sabbath?
Answer: August 1969