Thanks, everyone! Found this info:
Trapunto, or “stuffed work” was traditionally worked by hand, usually after a quilt was layered and quilted. In areas to be stuffed, the threads of the backing were pushed apart, or even cut, to create a hole large enough to stuff batting into the space in between the top and backing and inside the quilted lines. Special needles and other tools were used to push batting or cording into small spaces or quilted channels. This extra batting created textured motifs on the front of the quilt.