Murder ballads have long been a genre. But, I know what you mean about a trigger. When I first read her history, I couldn't believe I had never heard it before – she admitted to four hundred or more murders of babies, for cripes sake. And, it happened over decades before she was caught. That's the thing that struck me the most – for decades, that many babies didn't matter enough for them to actually do anything about it.
I found the history researching for my poetry series, "Twisted Nursery Rhymes." I never did find anything particularly dark about the originating nursery rhyme. But, most children's nursery rhymes have pretty dark inspirations – so dark in fact that they are little removed from murder ballads.
Thanks for coming back to leave your response after you were triggered. I appreciate it must have been difficult for you.