filled with brothers must have known more than girls raised in other circumstances, through overhearing conversations or being teased. This is obviously something that neither side can prove or disprove...mostly a matter of opinion. But even if Jane Austen didn't understand the reference, surely someone would have at some point before publication and explained it to her? I would not assume that just because, as far as we know, Jane Austen lived and died a virgin that also meant that she was totally ignorant of sexual matters. If she had lived a few decades later, I could then believe that, but as others have pointed out extreme prudery was not the fashion in her lifetime.