A childhood belief about general

I was about eight when I first saw the movie "Titanic" and I didn't know what a prostitute was. The scene where Jack shows Rose his drawings, he explains he didn't have an affair with that woman, "just her hands. See, she was a...one-legged prostitute." I asked mom what a prostitute was, and she just said it was a person that sold their bodies. She didn't say this meant sex, she just said selling their bodies. And since the one example of a prostitute I had came from the movie, and she had one leg, naturally I assumed it meant she sold her leg. For the longest time I thought prostitutes cut off body parts and sold them, until a 5th grader clued me in.