Why is "générique" the word used in French to refer to the credits/title sequence/theme song of a T.V. show or movie? How did "générique" come to acquire such a meaning? So far, I've had zero luck trying to determine how exactly this specific use of the word could have possibly come about, seeing as its etymology and other definitions have otherwise no obvious relation to the notion of "theme song" that might explain the confusing semantics.

Any and all input is much appreciated! Merci d'avance~