A tannis root is a root of a fictional herb that is enclosed in a locket in the move the 1968 movie, "Rosemary's Baby." In the movie, the tannis root is enclosed in a locket of a character named Terry, which was given to her by the Castevets. The tannis root was described as being mysterious, smelly and noxious.
Rosemary, the main character in the movie, admired the locket that contained the tannis root worn by Terry. Later on, Terry would kill herself and the Castevets give her locket to Rosemary, telling her it was a good luck charm.
"Rosemary's Baby" is a horror film, which starred Mia Farrow as the title character and was directed by Roman Polanski. The film was based on the novel of Ira Levin with the same title.