The name "Frankenstein" is famous enough to have entered popular culture, even if people often get confused about whether it refers to the scientist or the monster. But where did Mary Shelley get this name from? Did it come from a particular real-life person, a local legend from somewhere in Europe, some significant hidden meaning? Surely it's more than just a random German-sounding name?
An easy might-be-true answer is in Wikipedia: from Burg Frankenstein, a castle in Germany, where your predecessors conjectured Shelley visited and possibly drew inspiration from the castle's legends.
This story is not universally believed, however. See the essay "Frankenstein – the monster’s home?" by Michael Mueller for a forceful denial of every insinuation found in the Wikipedia article.