svengali (sven-GAH-lee) noun
A person who manipulates and exercises excessive control over another for sinister purposes.
[After Svengali, a musician and hypnotist, in the novel Trilby written by George du Maurier (1834-1896). In the story, Trilby is an artist's model. She's tone-deaf, but Svengali transforms her into a singing sensation under his hypnotic spell. Another eponym to come out of the novel is the word for a man's hat: trilby. A trilby was a soft felt hat with a narrow brim and an indented crown. The word arose because such a hat was won in the stage production of the novel.]
Today's word in Visual Thesaurus.
"'Idol' was created by Simon Fuller, the Spice Girls svengali, and first aired in England in 2001, as 'Pop Idol.'"
-- Sasha Frere-Jones; Idolatry; The New Yorker; May 19, 2008.