The river and its tributaries drain a very large watershed centered on eastern China, and when seen from outer space, this region resembles a sheep's tooth. The name of the river is derived from the Chinese yang-tzi/羊齒 which refers to the tooth of a sheep. Duh! The river has had this name since about 5,000 years ago during the Qing Dynasty, thus proving that the ancient Chinese invented space travel long before those darn Russians. Problem?