I know the question's closed now, but I'm thinking maybe "the beginnings of denim" would work here. It's different from "the origin of denim", so it really depends on what you want to say in your document.
In my opinion (as a non-native speaker), the "origin of denim" is about what denim came from, what it was before turning into the jeans clothes we know, while "the beginnings of denim" is about the early history of the use of denim in clothing.

There's an example here:

Ever since the beginnings of denim in the 1800’s till the late 1970’s, denim was universally made on machines known as shuttle looms.
forum.kitmeout.com/talk-fashion/1680-shuttle-loomed-denim.html