"You are not your f***ing khakis" - What does "khakis" exactly mean in the Fight Club movie?

"Khakis" is often used to refer to pants (that are khaki-colored, or made of the khaki textile). For example, Old Navy has a khakis page that lists various pants and one specific to men's khakis.

In the context of the movie, khakis are another 'material good' that Tyler denounces, like cars, ikea furniture, etc.

Maybe I have a clue. Sir Terence Conran, a founder of Habitat, an advocate of design and minimalism, supposedly said, "I am not my khakis"

Meaning:

The stuff you own, wear, etc. does not define you. This is not about a higher status symbol. This is just about things / stuff in general. I suppose the minimalistic rhetoric of Fight Club refers to this sentense, because it is a symbol of not beeing addicted to material posessions.

The character Tyler Durden is referring to a popular commercial (late 1990's) from The Gap clothing company. It showed people dancing to swing music (a retro trend at the time) to promote their khakis pants. His line is mocking the vapid materialistic commercialism of the era. Which is sadly tame compared to now in 2021.