May have ventured through the rabbit hole about candaulism, and here are a few anecdotes:
It’s named after a king showing off his wife to his bodyguard. He didn’t get consent, she found out, and told the bodyguard to either kill the king or be killed himself. Welp, at least they made it into the history books.
Extramarital sex used to be called “criminal conversation”, abbreviated crim. con. I just need that to be used in some B-rated movie by an underground hacker / history nerd putting out innuendos about flirting and planning to take the system down.

Sir Richard Worse-than-sly, exposing his wife’s bottom; - O fye!

A still from Il merlo maschio / The Male Blackbird, one of the earliest films where candaulism is explored (a cello player starts, consensually, showing off his wife as a target of proxy admiration towards him)