These are hilarious. I'm pretty sure I owned a couch made of the same material at one point in my life, and it was made in the 70s.
These are an imperfect fit on older Barbies and early 60's straight leg Kens. Waist band is a bit tight for Ken dolls (though they do snap closed) and a bit loose for Barbie. Not a clue what doll these pants were for originally, but they're too groovy not to post.