(Yagu)夜具 or bedclothes, is a good expression for these pants. They look like something made from bedding mixed with pillow cases. Basically work pants with repairs from scraps from bedding. Some hints of quilting and corduroy, I would say work-repair mixed with farm-repair. I imagine someone working on weaving, or textile machines to wear something like this. Nice addition to the spring-summer 2011.
I love this rear-pocket patch for the knee.
Fibers and a nicly contrasted knee-patch.