great migration
noun
1(Usually with the) any of the major or significant migratory movements of peoples in ancient or historic times.
2 NZ History (also with capital initials), (according to a Maori founding myth, now considered of doubtful historicity) the migration of Polynesian peoples in a fleet of canoes from Hawaiki to New Zealand in the 14th cent.; also called heke.
Origin
Mid 19th century; earliest use found in Henry Milman (1791–1868), historian and dean of St Paul's.