There is no established Korean Martial Art called "deon."
The closest term I can find to this spelling of "deon" in Korean is 던져 (deon Jye) which means "throw" or 던지기 (deon ji gi) which means "to throw." Therefore, itmight be a technique, and not a Martial Art.
I am not aware of any other such term in Korean by this spelling (perhaps an alternate English spelling would render a different Korean term).
"Deon" is typically spelled as "던" in Korean.
It is an South Korean martial art/sport
Tang soo do Hapkido Tae Kwon Do
No. Korea does have a similar martial art, but Aikido is Japanese.
There is no actual known founder of the Korean martial art Tang Soo Do, however the name for the art of Tang Soo Do was adopted by Hwang Kee, the person who founded Moo Duk Kwan.
No one "assigned" taekwondo as a Korean martial art. Taekwondo was developed by Koreans for Koreans in Korea.
Hapkido is a Korean Martial Art and Karate is an Okinawan Martial Art. Both involve learning strikes, grappling and throws.
Do jang is a Korean term. It refers to the school where the martial art is taught. In Japanese it is a dojo.
Taekwondo
They are martial arts from Asia. Karate is from Okinawa, and influenced the Korean art of Taekwondo.
Tang soo do. It is a Korean art and is a predecessor to Taekwondo.
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