"Bhujanga" means "cobra" in Sanskrit. This asana is called "Bhujangasana" as the raised trunk, neck and head while practicing it resemble a cobra rearing its hood and about to strike, while the joined and stretched legs resemble its tail.
"Chakra" means "wheel" in Sanskrit. In the final position of this asana, the body is arched backward and resembles the rim of a wheel. Hence the name.