Quoting from Jan Ellen Goldstein (). Console and Classify: The French Psychiatric Profession in the Nineteenth Century. University of Chicago Press. p. 155. ISBN0-226-30161-3.
"Idée fixe was also originally a medical term, probably coined by the phrenologists Gall and Spurzheim in connection with Esquirol's delineation of monomania; see their Anatomie et physiologie du système nerveux en général et du cerveau en particulier, Vol. 2 (Paris: F. Schoell, 1812), p. 192. It also was transferred to nonmedical culture, most notably by the composer Hector Berlioz..." The term leitmotif refers to the same musical device as idée fixe.
