Analysis of information sources in references of the Wikipedia article "Idée fixe (psychology)" in English language version.
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...
Some of the French alienists extend the use of the term [imperative idea] to actual delusion (idée fixe), as for instance, ideas of persecution. but it is to be hoped that [imperative idea] will be carefully restricted to that intellectual tyranny which the individual deplores and is not deluded by.