This was from “Myrddin (Mystic Wizard of the Net)”. It was published by Stan Kegel on the groaners listserv.

Jill on an airplane, strikes up a conversation with the geeky computer programmer sitting next to her.

“Where are you going?” asks Jill.

“I’m going to San Jose,” says the geek, “to a computer convention. We specialize in operating systems for large computers. Let me tell you all about it.”

Later, Jill’s husband picks her up at the airport. “How was the flight?” he asks.

“Oh, fine,” says Jill. “I sat next to this guy I felt really sorry for.”

“Why’d you feel sorry for him?”

“He didn’t have any testicles.”

“What?!” says the husband. “And just how did you learn *that*?”

“Because,” says Jill, “he said he was going to a eunuchs’ convention.”