I had a pair like this when I was in 5th grade. We used to call them elephant pants. There is no tags in these so I don’t know the size or brand. please look at pictures and measurements. So these pants are made out of an acrylic wool with a kind of poly knit backing. This was popular back in the late 60s and early 70s. The advantages of this fabric was that it was washable and did not shrink.

This item is sold from a vintage boutique in Ames, IA.