After an episode of Game of Thrones featuring a Grey Worm love scene, a passionate speech from Varys, and Theon reverting back into Reek mode, eunuchs are having a moment in Westeros. But if you're wondering what "eunuch" means, you're definitely not alone.
The term isn't often used in modern Western culture, but it does come with a certain amount of historical weight. Eunuch is a word used for someone who has been castrated, and it's applied to both people who have been partially castrated or fully. It's rare for a person to choose to become a eunuch, although it's not unheard of. Boys were generally cut before puberty, but the procedure can happen at any age, as Game of Thrones has shown. Historically, young boys were turned into eunuchs for religious reasons, to serve as soldiers and strategists (like the Unsullied), to guard harems, or for darker purposes, such as sex slavery. In some cultures, eunuchs are revered and considered "clean."
In the world of Game of Thrones, Varys is the most prominent eunuch in the series. He reveals to Tyrion in season three that he's fully castrated, meaning not only were his testicles removed, but so was his penis. Horrifically, he remains aware throughout the procedure, which is done by a sorcerer when he's just a boy. Like many real-life boys who become eunuchs, Varys is sold to a person who wants to use his body. Although he doesn't refer to himself as a slave — he simply says he was travelling with a troupe of actors — he does tell Tyrion his master is the one who sells him to the sorcerer. This horrible experience leads Varys to use thievery and blackmail to climb through society until he reaches a position where he can influence who sits on the Iron Throne.
While Varys is cut in service of some twisted spell, the Unsullied are born slaves with no purpose other than to fight. Most are born into the practice, but any slave boy can be cut before the age of 5. This prevents them from going through puberty and dampens any sexual urges they may have by lowering their testosterone levels. In theory, it also makes them less bloodthirsty and more rational on the battlefield. The Unsullied are put through rigorous training to prevent them from showing emotion or displaying any sense of individuality. Many of the young boys do not survive the process, which in the mind of those who purchase the soldiers means they're getting the best of the best.
However, it's not their lack of sex organs that make the Unsullied lose touch with their emotions; it's the brutality they are subjected to from childhood onward. As Grey Worm's love for Missandei illustrates, being a eunuch does not mean a man is asexual. Not much is known about the sex lives of eunuchs, but they can have them, and they can certainly experience emotions as strongly as anyone else.
The show's final prominent eunuch character is Theon Greyjoy, who is castrated by Ramsay Bolton in season three. Theon's late-in-life castration, as well as the extensive torture Ramsay puts him through, leaves him broken and suffering from post-traumatic stress disorder. His PTSD is so severe it causes him to leave his sister, Yara, in his Uncle Euron's grip during a raid on their fleet.
As you can see from Varys, Grey Worm, and Theon, the most important thing to know about the term eunuch is that the only thing it tells you about the person it's used to describe is that they have been castrated. Game of Thrones is delving deep into the psyches of these three very different men, and although they share a past trauma, they all take different approaches to life and sexuality. Being a eunuch doesn't define their stories — it's simply a part of them.