The word for today is…
idée fixe (noun) – A fixed idea; an obsession.
Source : The Free Dictionary
Etymology : The term idée fixe is a 19th-century French coinage. French writer Honoré de Balzac used it in his 1830 novella 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. Although it is still used in both psychology and music, nowadays idée fixe is also applied to milder and more pedestrian obsessions.
