Season 6 of Game of Thrones is only two episodes in but it's been all about the big revelations so far. In "Home," it was revealed via flashback that Bran's sidekick, gentle giant Hodor was actually not always Hodor-ing around; his real name is actually Wylis, and he used to be able to speak. This is a pretty big deal, because it opens up a lot of questions when it comes to who Hodor used to be and how he became the man of few words he is now. Some theories have emerged in the wake of this major reveal, and one particularly interesting article has delved into what might be going on with Hodor medically. What does Hodor mean on Game of Thrones?
As explained by Jordan Gaines Lewis for New York magazine, Hodor's particular problem might be something called "expressive aphasia." Aphasia is when people are no longer able to understand speech or communicate it effectively. Expressive aphasia results in the loss of most speech, with only a few key words or phrases lingering; this is also known as "telegraphic speech," where important parts of the intended sentence are spoken but minor unimportant words like "the" will be left out. If this is what is effecting Hodor, then he would be at the extreme end of it because there is only one word he is able to say.
Expressive aphasia was diagnosed first by a doctor named Paul Broca in France in 1861. He had a patient called Louis-Victor Leborgne whose cognitive functions were normal outside of his speech impairment; like Hodor, he was also only able to say one word, "tan." Broca's research led him to discover that a specific area of the brain was being affected, one that handles language comprehension and interpretation of gestures associated with language (waving hello or goodbye, for example). This area of the brain would have been damaged, either by a stroke, a tumor, or trauma, and the result could be expressive aphasia.
This has led fans to wonder what kind of event left Hodor in his current state. He was a stableboy, so it could be a hazard of the job like being kicked by a horse that led to his potential brain damage. However, Game of Thrones theories are rarely so simple – and it seems doubtful that certain important connections would have been made if there wasn't more to them than a run of the mill accident.
Hodor is most often in Bran's company, and fans are theorizing that their similarities go deeper than one might expect. It's possible that Hodor was witness to some information he shouldn't have known (like how Bran discovered Jaime and Cersei) and he was injured in the aftermath to prevent him telling anyone. The flashback showed he was close to Lyanna, so he might know something important about her abduction or death.
Another theory posits that Hodor is like Bran in a different way: he is also a warg. If a warg spends too long in the mind of an animal or the animal is injured while someone is warging into it, it could have adverse effects on the warg himself. If either of those things happened to Hodor, that could be why his speech is so limited now.
Unfortunately, the only one who would know is the only one not capable of telling. Unless Bran's continued trips to the past delve deeper into Hodor's history, this is one mystery that might stay with Hodor.