The mountain is called Pendle Mountain after Pendle Hill in England. In 1612, twelve people from the area around Pendle Hill were tried for witchcraft. Also, Mother Malkin was most likely named after Malkin Tower, the house where Demdike (one of the witches tried in the Lancashire Witch Trials in 1612) lived. Malkin was local slang for excrement at the time.
Warner Bros. was originally supposed to release the film as part of a long-running partnership with the film's producer, Legendary Entertainment. Advertising materials were already being made when both parties agreed to end the partnership, and Legendary affiliated with Universal Pictures, which is now distributing the film. This explains why early posters still contain the Warner Bros. logo.
The original plan was that the soundtrack would have been composed by Tuomas Kantelinen and A.R. Rahman but due to the production delays they dropped out in autumn 2013. Marco Beltrami was then brought in to score the movie.
The title Seventh Son is also part of the title of an album and song by Iron Maiden called Seventh Son Of A Seventh Son. In the movie Jeff Bridges says "You're the seventh son of the seventh son" which is also similair to the chorus line in the Iron Maiden song. The album is a concept album.