Have you done a google search for the common meaning of "stash"? Items hidden away, most commonly drugs, weapons, or ill-gotten money.
I was thinking about why people choose to call attention to the fact that a quilt is "scrappy" or "stash". Maybe it's a way of deflecting criticism -- I know that isn't a perfect color match, but it's a stash quilt. Or maybe it's to forestall comments about money spent-- yes, I know I said I was cutting back on credit card debt, but this is a *stash* quilt. Otherwise, it's just a descriptor, kind of like-- this is a Tula Pink Parisville quilt, and this is the scrappy one I did last year. . .