Hodor, hodor…Hodor—hodor, hodor—hodor.

Hrmm, <cough> I mean, what could possibly happen to the brain to make a single word your only communication?

In HBO’s Game of Thrones, the character known as “Hodor” isn’t called that because it’s his real name (it’s actually “Walder” according to the Song of Ice and Fire novels). Everyone calls him Hodor because that’s all he can say. While he can express emotions, follow commands, and act otherwise normally, something happened to Hodor’s brain long ago that reduced his vocabulary to almost nothing. But Hodor’s condition is much more than a plot device: it’s a real medical condition that was first described over 150 years ago.

French surgeon and physician Paul Broca was laying the groundwork of modern neuroscience in the 1860s. In 1861, Broca encountered two patients with significant speech difficulties that would get Broca a region of the brain named after the physician. The first patient, a 51-year old man, came to Broca severely impaired. Whenever the man tried to utter a word, the only thing that came out was “tan.” People came to call him that, too.

A few months later, Broca examined an 84-year old man who could only utter five words.

Both patients unfortunately passed away shortly thereafter, and upon their autopsies, Broca discovered what he had been expecting from his previous work—damage to the brain’s frontal lobes damaged speech. More specifically, Broca determined that lesions to the inferior frontal gyrus of the left cerebral hemisphere (front of your brain on the left side) significantly impacted speech. This area was later dubbed “Broca’s area” for his discovery, and impairments resulting from damage to that area were dubbed “Broca’s aphasia.” While neuroscience in the intervening centuries has refined and added to Broca’s findings, his initial discovery was a crucial part in our understanding of the way the brain localizes certain functions to certain areas. (It was also another nail in the coffin for dualism, but that’s a whole other debate.)

What does all this mean for Hodor? Writing at Mother Jones, neuroscientist Indre Viskontas describes the consequence of Broca’s findings and diagnoses the friendly giant:

“Hodor’s combination of impoverished speech production with relatively normal comprehension is a classic, albeit particularly severe, presentation of expressive aphasia, a neurological condition usually caused by a localized stroke in the front of the brain, on the left side. Some patients, however, have damage to that part of the brain from other causes, such as a tumor, or a blow to the head.”

It’s not clear what kind of brain damage made Hodor who he is in Game of Thrones, but outside of direct trauma or tumors, Viskontas speculates that malnutrition could also have caused his disorder. However, noting his prodigious girth, Viskontas doesn’t think that very likely.

So, Hodor has a real brain disorder, The Mountain really is a crusher, giants are incredibly strong, and dire wolves were fascinating creatures from only a few thousand years in the past. That’s a decent scientific track record for a show that hodor hodor hodor, hodor—hodor.

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Kyle Hill is the Chief Science Officer of the Nerdist enterprise. Follow the continued geekery on Twitter @Sci_Phile.

IMAGE: HBO