The story on which the film is based, "The Bridge to Body Island," has a much more complex mythology for the Bye Bye Man: He was an albino born in New Orleans in 1912 who ran away as a child and became a derelict who lived in a train yard. After going blind he began murdering people and cutting out their eyes and tongues, which he sewed together and brought to life using voodoo. The resultant creature became the Bye Bye Man's literal seeing-eye dog, helping him hunt his prey. Several elements from the story- notably the dog and the motif of trains-- were retained for the movie, though their purpose is left undefined.
Previously rated R by the MPAA for "bloody horror violence, language and some sexuality."
The coin, which is a recurring thematic throughout the movie is likely a reference to the obol from Greek mythology, where it was used to pay Charon, the ferryman of the river Styx (which separated the world of the living from the world of the dead) for safe passage to the underworld. It symbolizes (impending) death.
Filmed in November and December 2015, but not released until January 2017.
Doug Jones, who plays the title character, previously played Slender Man (who has similar abilities) in Always Watching: A Marble Hornets Story. He also starred as Billy Butcherson in "Hocus Pocus" and the amphibian man in "The Shape of Water".