Actually the translation of the Sanskrit name is Western Intense Stretch. Funny, huh?! It's because traditionally yoga is practiced in the morning while facing the rising sun therefore, the side of the body that receives the stretch is the West side. However it is called, it is one of the integral poses of many yoga systems, not only Ashtanga. And the anatomical alignment of the spine and the pelvis are the bases for every other forward bending pose whether it be Janusirsasana A, B or C or Krounchasana.