I think I first heard the expression "blank died the death of a rag doll" from my oldest sister, and I've always suspected it was passed down to her along the well-worn matrilineal pathways of old Irish sayings, like "whistling makes the Virgin Mary cry" and "this place is filthier than Hogan's Alley" (don't ask, I don't know). Of course, I'm not really sure where my sister got it, although I'm certain if I asked her, she'd blithely swear that she's never heard, let alone used the expression in her entire life. (My sister's like that. Happy to encourage your sense of insanity.)
It's perfect really: the best idioms have sort of poetic shorthand about them. They not only say something in less words than it would take to do so straightforwardly, they add a touch of the ineffable to the description, so that strangely, beautifully, they say something that's effectively impossible to say else wise.
Of course, if I had to come right out and prosaically define it, I'd say it's the slow passage into nonexistence of that which was once, however briefly, ardently embraced. The most obvious example is the rag doll herself. She was your favorite. You hugged her to your chest every night as you feel asleep, and then one night, either because you got a nicer stuffed toy, or because it dawned on you that sleeping with dolls is stupid, you put her at the bottom of your bed instead of hugging her to you. From there to underneath the bed, dusty and forgotten, is just a few sad, small steps. One day, she just disappears. Maybe Mom throws her out or gives her to Good Will, but it's of no concern to you. You haven't even noticed she's gone.
Once something ceases to be remembered, did it ever even exist at all?
Examples of things that can die the death of a rag doll:
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