Gonzetsu is a term which appears in many Japanese ancient documents, but until recently its true meaning and connection with Koshiabura were a mystery. The author has made clear the meaning of Gonzetsu and its connection with Koshiabura. Based on many ancient records and field investigations of Oshitsu in Korea. Until about the 11th century the name Gonzetsu referred to the sap of Koshiabura trees in Japan, and later called by the Japanese name Koshiabura. Oshitsu is a sap of Dendropanax morbifera Lev. Which was used in Korea as a painting material. The Koshiabura tree is A canthopanax sciadophylloides Frank et Sav.