I spent all morning preparing a class on swearing in Spanish. Obviously this is a topic I could spend even more time on it if I were a real expert. Camilo José Cela wrote an entire dictionary of obscenities. One volume is devoted exclusively to testicles. Another volume is on the penis. It's a little awkward because all nine students in the class are women. Really, though, obscenity is not (mostly) about sex at all. Sex is the vehicle of the metaphor.