scrim

noun

1. a cotton or linen fabric of open weave used for bunting, curtains, etc.
2. Theater. a piece of such fabric used as a drop, border, or the like, for creating the illusion of a solid wall or backdrop under certain lighting conditions or creating a semitransparent curtain when lit from behind.

noun

1. an open-weave muslin or hessian fabric, used in upholstery, lining, building, and in the theatre to create the illusion of a solid wall or to suggest haziness, etc, according to the lighting

n.“upholstery lining,” 1792, of unknown origin.