I guess it is a fairly recent term, though I have heard it for a while. After trying to find the origin of the word for quilting with not much success except the definition of the word (part of the definitions: "easily broken, torn, etc. : not strong or solid"), my guess is that the term started to be used in quilting because of the vulnerability of the raw edges and raw seams, a quilt top would be relatively flimsy, regardless of fabric quality, compared to a finished quilt.