A finish given to a fabric or garment to enable it to retain its creases, pleating, shape, smoothness, etc.; the process which produces this finish. Frequently attributive, designating fabrics and garments made with such a finish.
permanent press/ˌpəːmənənt ˈprɛs/ /ˌpəːm(ə)nənt ˈprɛs/
1940s; earliest use found in The Syracuse Herald-Journal. From permanent + press.