According to The New Grove Dictionary of Music and Musicians, the term "idée fixe" was coined by French composer Hector Berlioz in 1830, who used it to describe the principal theme of his Symphonie fantastique. That reference goes on to say that, at about the same time, French novelist Honore de Balzac used "idée fixe" in Gobseck to describe an obsessive idea. By 1836, Balzac's more generalized use of the term had carried over into English, where "idée fixe" was embraced as a clinical and literary term for a persistent preoccupation or delusional idea that dominates a person's mind. Nowadays "idée fixe" is also applied to milder and more pedestrian obsessions.
Examples of idée fixe in a Sentence
had this bizarre idée fixe that people were spying on her with electromagnetic waves