An image of Dragon(http://www.zakka.net/kouyuu/shouhin.php?shid=79680)
A dragon is an imaginary and mysterious animal which ancient people used to fear and worship in Japan.
Ashikawa Keishu (life history unknown) wrote a book titled "Byoumeiikai" (Collected Explanations of Disease Names) in 1686 during the Edo period (1603-1868).
He arranged the name list of 1822 diseases in all in iroha order (similar to the alphabetical order) and explained each.
In the book, he states about deafness:
"Dragon hears sound on the horns instead of the ears which it doesn't have".
In addition, the sea horse resembles the form of the dragon and the Japanese Federation of the Deaf makes it its official logo.
A sea horse(http://starfort.cocolog-nifty.com/voorlihter/2008/05/post_e698.html)
The official logo of the Japanese Federation of the Deaf
(http://www.jfd.or.jp/)The word "Rou" which means "Deaf" is often written in kanji (a Chinese character), [聾]. Interestingly, you will see, it is composed of two Chinese characters [龍], which means a dragon, and [耳] meaning an ear.