"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.
"Danda" means "stick" in Sanskrit.
"Shalabha" means "locust" in Sanskrit. The final position of this asana resembles a locust when it lowers its head to eat and raises its tail. Hence, the name.
"Sukha" means "pleasant" or "comfortable" in Sanskrit. Any cross-legged sitting position which you find comfortable, in which the body does not shake and in which you can remain at ease for a long time, is called Sukhasana.
This pose is also called Downward Dog or Downward-Facing Dog.