Why King Cobra called as "King" ?

The King Cobra (Ophiophagus hanna) is the largest poisonous snake,  the Latin word Ophiophagus means "Snake-eater". The king cobra can reach a length of around 18.5ft , and lives in the Rainforest's and grasslands of Southeast Asia, India and China. The King cobra is very fast and the average lifespan is about 20 years. It is called “King” because it is the only species in snakes which can eat its own poisonous species, the poison of its species does not make any effect on its body. The king cobra is not the most poisonous snakes but it can kill an elephant with one bite, the king cobra kills it's prey by striking and injecting it with venom and swallowing it whole, it normally feed on other venomous and non-venomous snakes but includes small reptiles, birds and amphibians as well. The only predators are the mongoose and man.