I'll risk showing my own ignorance, to let it serve as a probably-typical bad example. When I saw the name Dick Turpin, I immediately knew I had heard it occasionally, but I was thinking he was a comedian in silent movies. After I got into the thread, I realized I had heard of him and "Black Bess" a few times, but I couldn't have placed him within a century of the correct dates. I've never known any of the songs about him.