Hodor hodor hodor . Hodor hodor ? Hodor . Hodor-hodor . Hodor ! While this sentence might puzzle many , fans of the hit HBO show Game of Thrones , the fifth season of which had its US premiere last night , will understand the reference . Hodor is the brawny , simple-minded stableboy of the Stark family in Winterfell . His defining characteristic , of course , is that he only speaks a single word : 'Hodor . ' Hodor , a character in Game of Thrones , earned his name because he says only the word 'Hodor ' over and over again . He may have expressive aphasia , according to Jordan Lewis , of Penn State Medical School . But those who read the A Song of Ice and Fire book series by George R R Martin may know something that the TV fans do n't : his name is n't actually Hodor . According to his great-grandmother Old Nan , his real name is Walder . 'No one knew where 'Hodor ' had come from , ' she says , 'but when he started saying it , they started calling him by it . It was the only word he had . ' Whether he intended it or not , Martin created a character who is a textbook example of someone with a neurological condition called expressive aphasia . LOSING THE ABILITY TO SPEAK . In 1861 , French physician Paul Broca was introduced to a man named Louis-Victor Leborgne . While his comprehension and mental functioning remained relatively normal , Mr Leborgne progressively lost the ability to produce meaningful speech over a period of 20 years . Like Hodor , the man was nicknamed Tan because he only spoke a single word : 'Tan . ' Just a few days after meeting Dr Broca , Leborgne passed away . Dr Broca 's autopsy determined tissue damage , or a 'lesion ' , in the frontal lobe of Mr Leborgne 's left brain hemisphere , just next to a brain fold called the lateral sulcus . In 1861 , a French physician called Dr Broca found a particular part of the brain is involved in language . It became known as Broca 's area ( pictured in red ) . Damage to Broca 's area causes language problems . Over the next two years , Dr Broca acquired brains from 12 more patients with Mr Leborgne 's symptoms – all of the autopsy evidence was strikingly consistent . Neuroscientists are still examining this small region of the brain , now often referred to as 'Broca 's area ' to work out its many functions . Most research has focused on a patient 's inability to form syntactically complex sentences when this area is damaged . More recent work using functional magnetic resonance imaging ( fMRI ) has also reported that Broca 's area is active during language comprehension tasks , interpretation of movement and comprehending various gestures also associated with speech , such as waving goodbye . HOW BRAIN DAMAGE AFFECTS SPEECH . In collaboration with French scientists in 2007 , a group at the University of California revisited the brains of Mr Leborgne and Mr Lelong ( another of Mr Broca 's patients who could only speak five words ) using MRI scans . One of their most interesting findings was that their lesions extended much deeper than Broca had reported , suggesting that multiple brain regions were probably contributing to their speech deficits . This evidence of widespread damage is unsurprising . Mr Leborgne , Mr Lelong – and even Hodor – are actually more extreme examples of individuals with expressive aphasia . The new series of Game of Thrones , featuring Hodor , played by Kristian Nairns , aired yesterday . More commonly , a person with the disorder will express themselves in 'telegraphic speech ' , which usually comprises three or so words , including a noun and a verb . For example , someone may say , 'Anne , dog , walk ' to mean ' I walked the dog with Anne today . ' The most common cause of expressive aphasia is stroke , which occurs when a blood clot blocks a vessel in the brain , resulting in tissue damage due to lack of oxygen . It 's estimated that expressive aphasia occurs in 12 per cent of stroke patients , while roughly 35 per cent of stroke patients suffer from a language aphasia of some form . Expressive aphasia can also be caused by a tumour , haemorrhage , a haematoma in the membrane covering of the brain , or trauma to the head . It has been reported that Mr Leborgne suffered from epileptic seizures as a child – some have speculated that he may have experienced head trauma during one such episode . So what 's Hodor 's story ? Did he sustain a blow to the head , suffer a stroke , or was he simply a giant baby dropped by his mother ? He may only speak one word , but like the other characters in the show , Hodor too may have a quite an interesting backstory .
Penn State Medical School is a character in Game of Thrones who only speaks a single word . Expert says he may have the neurological condition expressive aphasia . This is where there is a lesion in the part of the brain that controls speech . Condition usually caused by a blow to the head , stroke or a tumour .