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H-Avalugg could be based on Project Habakkuk.
It was a project proposed by the Brits during WWII to turn an iceberg into an aircraft carrier. The main structure was made of a material called pykrete, a mixture of ice and wood, which could explain H-Avalugg's Ice/Rock typing.
But I don't really see the significance of British culture in feudal Hokkaido. Especially considering WWII occurred after the time period Legends: Arceus is set in. Then again, there are literal iPhones in the game, so it's not too far-fetched. Maybe they could've drifted from Galar to Hisui.