1) The history of momo in Nepal dates back to as early as the fourteenth century. Momo was initially a Newari food in the Katmandu valley. It was later introduced to Tibet, China and as far away as Japan by a Nepalese princess who was married to a Tibetan king in the late fifteenth century
2) It is not clear how momo invaded India, but it probably became popular with the influx of Tibetans in India. On the other hand, momo are extremely popular in Nepal, and a theory also says that it was the Newar merchants of Kathmandu who brought the recipe from Tibet during their trades.
3) Momos are a traditional delicacy in Bhutan, Nepal, Sikkim, Assam and now a days we can see that momos are widely spread all over the world.