Why go
Understanding the names helps explain why older accounts, museums and maps may describe the same region differently. Ainu Mosir means the land where people live in the Ainu language. Ezochi was a Japanese name used before the Meiji government adopted Hokkaido. The change in vocabulary reflects a change in political control, not simply a new label for an unchanged place.
The full story
Long before the name Hokkaido appeared, Ainu communities knew their homeland as Ainu Mosir, meaning the land where people live. Japanese speakers used Ezo for the people of the north and Ezochi for their land. Those terms appear in accounts of trade and contact across the strait between Hokkaido and Honshu. In the Meiji period, the government considered a new name as it expanded its administration of the island. Explorer Matsuura Takeshirō proposed several possibilities, including a form that became Hokkaido. His explanation linked part of that proposal to a supposed Ainu self-name, though that etymology has been disputed. The names therefore tell different stories: an Indigenous understanding of home, an outside label used during centuries of contact, and a state name adopted during a period of major change. Keep that distinction in mind when a museum or historic account uses Ezo rather than Hokkaido.